Editing Appendicitis (section)

==Diagnosis==
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The physician will ask questions to get the [[health history]], assess the patient's [[Signs and symptoms|symptoms]], do a complete [[Physical examination|physical exam]], and order both laboratory and imaging tests.<ref name=NIDDK>National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). (n.d.). Appendicitis – Diagnosis. Retrieved September 21, 2023, from https://www.niddk.nih.gov/health-information/digestive-diseases/appendicitis/diagnosis</ref> Appendicitis symptoms fall into two categories, typical and atypical.<ref name="typical"/>

Typical appendicitis is characterized by a migratory right [[iliac fossa]] pain associated with nausea, and anorexia, which can occur with or without vomiting and localized muscle stiffness/ generalized [[Abdominal guarding|guarding]].<ref name=typical>{{cite journal |last1=Echevarria |first1=S |last2=Rauf |first2=F |last3=Hussain |first3=N |last4=Zaka |first4=H |last5=Farwa |first5=UE |last6=Ahsan |first6=N |last7=Broomfield |first7=A |last8=Akbar |first8=A |last9=Khawaja |first9=UA |title=Typical and Atypical Presentations of Appendicitis and Their Implications for Diagnosis and Treatment: A Literature Review. |journal=Cureus |date=April 2023 |volume=15 |issue=4 |pages=e37024 |doi=10.7759/cureus.37024 |doi-access=free |pmid=37143626|pmc=10152406 }}</ref> It is possible the pain could localize to [[Left lower quadrant|the left lower quadrant]] in people with [[situs inversus totalis]].<ref>{{cite journal |last1=Oh |first1=JS |last2=Kim |first2=KW |last3=Cho |first3=HJ |title=Left-sided appendicitis in a patient with situs inversus totalis. |journal=Journal of the Korean Surgical Society |date=September 2012 |volume=83 |issue=3 |pages=175–178 |doi=10.4174/jkss.2012.83.3.175 |pmid=22977765|pmc=3433555 }}</ref> The combination of migrated [[Umbilical region|umbilical]] pain to the right [[Quadrants and regions of abdomen|lower quadrant]], loss of appetite for food, nausea, unsustained [[vomiting]], and mild [[fever]] is classic.<ref name="typical" />

Atypical histories lack this typical progression and may include pain in the right lower quadrant as an initial symptom. Irritation of the peritoneum (inside lining of the abdominal wall) can lead to increased pain on movement, or jolting, for example going over [[speed bump]]s.<ref>{{cite journal | vauthors = Ashdown HF, D'Souza N, Karim D, Stevens RJ, Huang A, Harnden A | title = Pain over speed bumps in diagnosis of acute appendicitis: diagnostic accuracy study | journal = BMJ | volume = 345 | issue = dec14 14 | pages = e8012 | date = December 2012 | pmid = 23247977 | pmc = 3524367 | doi = 10.1136/bmj.e8012 }}</ref> Atypical histories often require imaging with ultrasound or CT scanning.<ref name=Hob1998/>

===Signs===
During the early stages of appendicitis diagnosis, it is common for [[Physical examination|physical exams]] to present inconspicuous findings. Signs of inflammation become noticeable as the disease progresses. These signs may include<ref>Jones MW, Lopez RA, Deppen JG. Appendicitis. [Updated 2023 April 24]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan. Available from: https://www.ncbi.nlm.nih.gov/books/NBK493193/</ref>
* [[Aure-Rozanova's sign]]: Increased pain on palpation with a finger in the right [[Lumbar triangle|inferior lumbar triangle]] (can be a positive [[Blumberg's sign]]).<ref name="SachdevaDutta2012">{{cite book|last1=Sachdeva|first1=Anupam|last2=Dutta|first2=AK|title=Advances in Pediatrics|date= 2012|publisher=JP Medical |isbn=978-93-5025-777-7|page = 1432}}</ref>
* [[Bartomier-Michelson's sign]]: Increased pain on palpation at the right iliac region as the person being examined lies on their left side compared to when they lie on their back.<ref name="SachdevaDutta2012"/>
* [[Dunphy's sign]]: Increased pain in the right lower quadrant by coughing.<ref name=Sign>{{cite book |last1=Al-Salem |first1=Ahmed H. |title=Atlas of Pediatric Surgery: Principles and Treatment |date=2020 |publisher=Springer |location=Cham |isbn=978-3-030-29210-2 |edition=1st }}</ref>
* [[Hamburger sign]]: The patient refuses to eat ([[anorexia (symptom)|anorexia]] is 80% [[Sensitivity and specificity|sensitive]] for appendicitis)<ref name="VirgilioFrank2015">{{cite book|last1=Virgilio|first1=Christian de|last2=Frank|first2=Paul N.|last3=Grigorian|first3=Areg|title=Surgery|date= 2015|publisher=Springer|language=en |isbn=978-1-4939-1726-6|page = 215}}</ref>
* [[Kocher's sign (appendicitis)|Kocher's sign]] (Kosher's sign): From the person's medical history, the start of pain in the umbilical region with a subsequent shift to the right iliac region.<ref name="SachdevaDutta2012"/>
* [[Massouh's sign]]: Developed in and popular in southwest England, the examiner performs a firm swish with their index and middle finger across the abdomen from the [[xiphoid process]] to the left and the right iliac fossa.<ref name="Sign"/>
* [[Obturator sign]]: The person being evaluated lies on her or his back with the hip and knee both flexed at ninety degrees. The examiner holds the person's ankle with one hand and knee with the other hand. The examiner rotates the hip by moving the person's ankle away from their body while allowing the knee to move only inward. A positive test is pain with internal rotation of the hip.<ref name="WolfsonCloutier2014">{{cite book|last1=Wolfson|first1=Allan B.|last2=Cloutier|first2=Robert L.|last3=Hendey|first3=Gregory W.|first4=Louis J.|last4=Ling|first5=Jeffrey J.|last5=Schaider|first6=Carlo L.|last6=Rosen|title=Harwood-Nuss' Clinical Practice of Emergency Medicine|url=https://books.google.com/books?id=cgMYBQAAQBAJ&pg=PT5810|access-date=15 June 2016|date= 2014|publisher=Wolters Kluwer Health|language=en|isbn=978-1-4698-8948-1|page = 5810|quote=Physical signs classically associated with acute appendicitis include Rovsing sign, psoas sign, and obturator sign.|url-status=live|archive-url=https://web.archive.org/web/20170910171627/https://books.google.com/books?id=cgMYBQAAQBAJ&pg=PT5810|archive-date=10 September 2017}}</ref>
* [[Psoas sign]], also known as "Obraztsova's sign", is right lower-quadrant pain that is produced with either the passive extension of the right hip or by the active flexion of the person's right hip while supine. The pain that is elicited is due to inflammation of the peritoneum overlying the iliopsoas muscles and inflammation of the psoas muscles themselves. Straightening out the leg causes pain because it stretches these muscles while flexing the hip activates the iliopsoas and causes pain.<ref name="WolfsonCloutier2014"/>
* [[Rovsing's sign]]: Pain in the lower right abdominal quadrant with continuous deep palpation starting from the left [[iliac fossa]] upwards (counterclockwise along the colon). The thought is there will be increased pressure around the appendix by pushing bowel contents and air toward the [[ileocaecal valve]] provoking right-sided abdominal pain.<ref>{{cite journal |last=Rovsing |first=N.T. |date=1907 |title=Indirektes Hervorrufen des typischen Schmerzes an McBurney's Punkt. Ein Beitrag zur diagnostik der Appendicitis und Typhlitis |journal=Zentralblatt für Chirurgie |location=Leipzig |volume=34 |pages=1257–1259|language=de}}</ref>
* [[Rosenstein's sign]] (Sitkovsky's sign): Increased pain in the right iliac region as the person is being examined lies on their left side.<ref name="DunsterHunter1922">{{cite book|last1=Dunster|first1=Edward Swift|last2=Hunter|first2=James Bradbridge|last3=Sajous|first3=Charles Euchariste de Medicis|first4=Frank Pierce |last4=Foster |first5=Gregory |last5=Stragnell |first6=Henry J. |last6=Klaunberg |first7=Félix |last7=Martí-Ibáñez |title=International Record of Medicine and General Practice Clinics|year=1922|publisher=New York Medical Journal |language=en|pages = 663}}</ref>
* Perman's sign: In acute appendicitis palpation in the left iliac fossa may produce pain in the right iliac fossa.<ref>Emil Samuel Perman (1856–1946), "About the indications for surgery in appendicitis and an account of cases of Sabbatsberg Hospital in Hygiea, 1904.</ref>

===Laboratory tests===

While there is no laboratory test specific for appendicitis, a [[complete blood count]] (CBC) is done to check for signs of infection or inflammation. Although 70–90 percent of people with appendicitis may have an elevated [[white blood cell count|white blood cell (WBC) count]], many other abdominal and pelvic conditions can cause the WBC count to be elevated.<ref name=CDEM>{{cite web|title=Appendicitis |first=Charmaine |last=Gregory |work=CDEM Self Study Modules |publisher=Clerkship Directors in Emergency Medicine |date=2010 |url=http://www.cdemcurriculum.org/ssm/gi/appy/appy.php |url-status=usurped |archive-url=https://web.archive.org/web/20131130062201/http://www.cdemcurriculum.org/ssm/gi/appy/appy.php |archive-date=2013-11-30 }}</ref> However, a high [[White blood cell count|WBC count]] may not alone represent a solid indicator of appendicitis but rather an inflammation<ref name=Shogilev2014 /> but the neutrophil ratio was more sensitive and specific for acute appendicitis.<ref>{{cite journal |last1=Şahbaz |first1=NA |last2=Bat |first2=O |last3=Kaya |first3=B |last4=Ulukent |first4=SC |last5=İlkgül |first5=Ö |last6=Özgün |first6=MY |last7=Akça |first7=Ö |title=The clinical value of leucocyte count and neutrophil percentage in diagnosing uncomplicated (simple) appendicitis and predicting complicated appendicitis. |journal=Ulusal Travma ve Acil Cerrahi Dergisi = Turkish Journal of Trauma & Emergency Surgery|date=November 2014 |volume=20 |issue=6 |pages=423–426 |doi=10.5505/tjtes.2014.75044 |pmid=25541921|doi-access=free }}</ref> Several routine and non-routine laboratory tests have been investigated for discriminating simple and complicated appendicitis, but their diagnostic accuracy is uncertain.<ref>{{Cite journal |last1=Sikander |first1=Binyamin |last2=Rosenberg |first2=Jacob |last3=Fonnes |first3=Siv |date=May 2023 |title=Individual biomarkers in the blood are not yet applicable in diagnosing complicated appendicitis: A scoping review |url=https://linkinghub.elsevier.com/retrieve/pii/S0735675723000839 |journal=The American Journal of Emergency Medicine |language=en |volume=67 |pages=100–107 |doi=10.1016/j.ajem.2023.02.016|pmid=36842426 }}</ref>

In children, [[Neutrophil to lymphocyte ratio|neutrophil-lymphocyte ratio (NLR)]] demonstrates a high degree of accuracy in the diagnosis of acute appendicitis and distinguishes complicated appendicitis from simple appendicitis.<ref>{{cite journal |last1=Prasetya |first1=D |last2=Rochadi |last3=Gunadi |title=Accuracy of neutrophil lymphocyte ratio for diagnosis of acute appendicitis in children: A diagnostic study. |journal=Annals of Medicine and Surgery |date=December 2019 |volume=48 |pages=35–38 |doi=10.1016/j.amsu.2019.10.013 |pmid=31687137|pmc=6820073 }}</ref> 75–78 percent of the patients have [[neutrophilia]].<ref name="Sign"/> Delta-neutrophil index (DNI) is a valuable parameter that helps in the diagnosis of histologically normal appendicitis and distinguishing between simple and complicated appendicitis.<ref>{{cite journal |last1=Shin |first1=DH |last2=Cho |first2=YS |last3=Cho |first3=GC |last4=Ahn |first4=HC |last5=Park |first5=SM |last6=Lim |first6=SW |last7=Oh |first7=YT |last8=Cho |first8=JW |last9=Park |first9=SO |last10=Lee |first10=YH |title=Delta neutrophil index as an early predictor of acute appendicitis and acute complicated appendicitis in adults. |journal=World Journal of Emergency Surgery|date=2017 |volume=12 |pages=32 |doi=10.1186/s13017-017-0140-7 |pmid=28747992 |pmc=5525197 |doi-access=free }}</ref>

A [https://medlineplus.gov/lab-tests/c-reactive-protein-crp-test/ C-reactive protein (CRP) blood test] will be ordered by the doctor to find out if there are any further causes of inflammation.<ref name="NIDDK" /> The C-reactive protein/albumin (CRP/ALB) ratio can be a reliable predictor of complicated appendicitis.<ref>Zhao, X., Yang, J. and Li, J. (2023) The predictive value of the C-reactive protein/albumin ratio in adult patients with complicated appendicitis. Journal of Laboratory Medicine. https://doi.org/10.1515/labmed-2023-0069</ref>

The [[urinalysis]] is important for ruling out a urinary tract infection as the cause of abdominal pain. The presence of more than 20 WBC per high-power field in the urine is more suggestive of a urinary tract disorder.<ref name=CDEM/>

If the patient is a female, a [[pregnancy test]] will be ordered.<ref name="NIDDK" />

===Imaging===
In children, the clinical examination is important to determine which children with abdominal pain should receive immediate surgical consultation and which should receive diagnostic imaging.<ref name="pmid17652298">{{cite journal | vauthors = Bundy DG, Byerley JS, Liles EA, Perrin EM, Katznelson J, Rice HE | title = Does this child have appendicitis? | journal = JAMA | volume = 298 | issue = 4 | pages = 438–451 | date = July 2007 | pmid = 17652298 | pmc = 2703737 | doi = 10.1001/jama.298.4.438 | author-link2 = Julie Story Byerley }}</ref> Because of the health risks of exposing children to radiation, ultrasound is the preferred first choice with CT scan being a legitimate follow-up if the ultrasound is inconclusive.<ref name="ACRfive">{{Citation |author1 = American College of Radiology |author1-link = American College of Radiology |title = Five Things Physicians and Patients Should Question |publisher = [[American College of Radiology]] |work = Choosing Wisely: an initiative of the [[ABIM Foundation]] |url = http://choosingwisely.org/wp-content/uploads/2012/04/5things_12_factsheet_Amer_Coll_Radiology.pdf |access-date = August 17, 2012 |url-status = live |archive-url = https://web.archive.org/web/20120416220509/http://choosingwisely.org/wp-content/uploads/2012/04/5things_12_factsheet_Amer_Coll_Radiology.pdf |archive-date = April 16, 2012 }}</ref><ref name="effectiveusct">{{cite journal | vauthors = Krishnamoorthi R, Ramarajan N, Wang NE, Newman B, Rubesova E, Mueller CM, Barth RA | title = Effectiveness of a staged US and CT protocol for the diagnosis of pediatric appendicitis: reducing radiation exposure in the age of ALARA | journal = Radiology | volume = 259 | issue = 1 | pages = 231–239 | date = April 2011 | pmid = 21324843 | doi = 10.1148/radiol.10100984 | doi-access =  }}</ref><ref name="appendicitischildren">{{cite journal | vauthors = Wan MJ, Krahn M, Ungar WJ, Caku E, Sung L, Medina LS, Doria AS | title = Acute appendicitis in young children: cost-effectiveness of US versus CT in diagnosis – a Markov decision analytic model | journal = Radiology | volume = 250 | issue = 2 | pages = 378–386 | date = February 2009 | pmid = 19098225 | doi = 10.1148/radiol.2502080100 | doi-access =  }}</ref> CT scan is more accurate than ultrasound for the diagnosis of appendicitis in adults and adolescents. CT scan has a [[sensitivity (tests)|sensitivity]] of 94%, [[Specificity (tests)|specificity]] of 95%. Ultrasonography had an overall [[sensitivity (tests)|sensitivity]] of 86%, a [[Specificity (tests)|specificity]] of 81%.<ref>{{cite journal | vauthors = Terasawa T, Blackmore CC, Bent S, Kohlwes RJ | title = Systematic review: computed tomography and ultrasonography to detect acute appendicitis in adults and adolescents | journal = Annals of Internal Medicine | volume = 141 | issue = 7 | pages = 537–546 | date = October 2004 | pmid = 15466771 | doi = 10.7326/0003-4819-141-7-200410050-00011 | s2cid = 46371675 }}</ref>

====Ultrasound====
[[File:SonoAppendizitis.JPG|thumb|An [[ultrasound]] image of acute appendicitis in December 2008]]
[[Abdominal ultrasonography]], preferably with [[doppler sonography]], is useful to detect appendicitis, especially in children. Ultrasound can show the free fluid collection in the right iliac fossa, along with a visible appendix with increased blood flow when using color Doppler, and noncompressibility of the appendix, as it is essentially a walled-off abscess. Other secondary sonographic signs of acute appendicitis include the presence of echogenic mesenteric fat surrounding the appendix and the acoustic shadowing of an appendicolith.<ref name="ReferenceA">{{cite journal | vauthors = Reddan T, Corness J, Mengersen K, Harden F | title = Ultrasound of pediatric appendicitis and its secondary sonographic signs: providing a more meaningful finding | journal = Journal of Medical Radiation Sciences | volume = 63 | issue = 1 | pages = 59–66 | date = March 2016 | pmid = 27087976 | pmc = 4775827 | doi = 10.1002/jmrs.154 | author3-link = Kerrie Mengersen }}</ref> In some cases (approximately 5%),<ref>{{cite journal|vauthors=Reddan T, Corness J, Mengersen K, Harden F|title=Sonographic diagnosis of acute appendicitis in children: a 3-year retrospective|journal=Sonography|volume=3|issue=3|pages=87–94|date=June 2016|doi=10.1002/sono.12068|s2cid=78306243|doi-access=free}}</ref> ultrasonography of the [[iliac fossa]] does not reveal any abnormalities despite the presence of appendicitis. This false-negative finding is especially true of early appendicitis before the appendix has become significantly distended. Also, false-negative findings are more common in adults where larger amounts of fat and bowel gas make visualizing the appendix technically difficult. Despite these limitations, sonographic imaging with experienced hands can often distinguish between appendicitis and other diseases with similar symptoms. Some of these conditions include [[inflammation]] of [[lymph nodes]] near the appendix or pain originating from other pelvic organs such as the ovaries or Fallopian tubes. Ultrasounds may be either done by the radiology department or by the emergency physician.<ref>{{cite journal |last1=Lee |first1=Sun Hwa |last2=Yun |first2=Seong Jong |title=Diagnostic performance of emergency physician-performed point-of-care ultrasonography for acute appendicitis: A meta-analysis |journal=The American Journal of Emergency Medicine |date=April 2019 |volume=37 |issue=4 |pages=696–705 |doi=10.1016/j.ajem.2018.07.025 |pmid=30017693|s2cid=51677455 }}</ref>

<gallery>
File:UOTW 45 - Ultrasound of the Week 1.webm|Ultrasound showing appendicitis and an appendicolith<ref name="UOTW45">{{cite web |date=25 April 2015 |title=UOTW #45 – Ultrasound of the Week |url=https://www.ultrasoundoftheweek.com/uotw-45/ |url-status=live |archive-url=https://web.archive.org/web/20170509131322/https://www.ultrasoundoftheweek.com/uotw-45/ |archive-date=9 May 2017 |website=Ultrasound of the Week}}</ref>
File:UOTW 45 - Ultrasound of the Week 3.jpg|Ultrasound showing appendicitis and an appendicolith<ref name=UOTW45/>
File:Ultrasonography of a normal appendix, annotated.jpg|Ultrasound of a normal appendix for comparison
File:Ultrasonography of a normal appendix without and with compression.jpg|A normal appendix without and with compression. Absence of compressibility indicates appendicitis.<ref name="ReferenceA"/>
</gallery>

====Computed tomography====
[[File:CAT scan demonstrating acute appendicitis.jpg|thumb|A CT scan demonstrating acute appendicitis (note the appendix has a diameter of 17.1 mm and there is surrounding fat stranding)]]
[[File:X-ray showing fecalith which has caused appendicitis.jpg|thumb|A [[fecalith]] marked by the arrow that has resulted in acute appendicitis.]]

Where it is readily available, [[computed tomography]] (CT) has become frequently used, especially in people whose diagnosis is not obvious on history and physical examination. Although some concerns about interpretation are identified, a 2019 Cochrane review found that the sensitivity and specificity of CT for the diagnosis of acute appendicitis in adults was high.<ref>{{Cite journal|last1=Rud|first1=Bo|last2=Vejborg|first2=Thomas S.|last3=Rappeport|first3=Eli D.|last4=Reitsma|first4=Johannes B.|last5=Wille-Jørgensen|first5=Peer|date=19 November 2019|title=Computed tomography for diagnosis of acute appendicitis in adults|journal=The Cochrane Database of Systematic Reviews|volume=2019|issue=11|doi=10.1002/14651858.CD009977.pub2|issn=1469-493X|pmc=6953397|pmid=31743429}}</ref> Concerns about radiation tend to limit use of CT in pregnant women and in children, especially with the increasingly widespread usage of MRI.<ref>{{cite journal | vauthors = Kim Y, Kang G, Moon SB | title = Increasing utilization of abdominal CT in the Emergency Department of a secondary care center: does it produce better outcomes in caring for pediatric surgical patients? | journal = Annals of Surgical Treatment and Research | volume = 87 | issue = 5 | pages = 239–244 | date = November 2014 | pmid = 25368849 | pmc = 4217253 | doi = 10.4174/astr.2014.87.5.239 }}</ref><ref>{{cite journal | vauthors = Liu B, Ramalho M, AlObaidy M, Busireddy KK, Altun E, Kalubowila J, Semelka RC | title = Gastrointestinal imaging-practical magnetic resonance imaging approach | journal = World Journal of Radiology | volume = 6 | issue = 8 | pages = 544–566 | date = August 2014 | pmid = 25170393 | pmc = 4147436 | doi = 10.4329/wjr.v6.i8.544 | doi-access = free }}</ref>

The accurate diagnosis of appendicitis is multi-tiered, with the size of the appendix having the strongest [[positive predictive value]], while indirect features can either increase or decrease sensitivity and specificity. A size of over 6&nbsp;mm is both 95% sensitive and specific for appendicitis.<ref>{{cite journal | vauthors = Garcia K, Hernanz-Schulman M, Bennett DL, Morrow SE, Yu C, Kan JH | title = Suspected appendicitis in children: diagnostic importance of normal abdominopelvic CT findings with nonvisualized appendix | journal = Radiology | volume = 250 | issue = 2 | pages = 531–537 | date = February 2009 | pmid = 19188320 | doi = 10.1148/radiol.2502080624 | doi-access =  }}</ref>

However, because the appendix can be filled with fecal material, causing intraluminal distention, this criterion has shown limited utility in more recent meta-analyses.<ref name="plumpy1">{{cite journal | vauthors = Doria AS, Moineddin R, Kellenberger CJ, Epelman M, Beyene J, Schuh S, Babyn PS, Dick PT | title = US or CT for Diagnosis of Appendicitis in Children and Adults? A Meta-Analysis | journal = Radiology | volume = 241 | issue = 1 | pages = 83–94 | date = October 2006 | pmid = 16928974 | doi = 10.1148/radiol.2411050913 }}</ref> This is as opposed to ultrasound, in which the wall of the appendix can be more easily distinguished from intraluminal feces. In such scenarios, ancillary features such as increased wall enhancement as compared to adjacent bowel and inflammation of the surrounding fat, or fat stranding, can be supportive of the diagnosis. However, their absence does not preclude it. In severe cases with perforation, an adjacent [[phlegmon]] or [[abscess]] can be seen. Dense fluid layering in the pelvis can also result, related to either [[pus]] or [[feces|enteric spillage]]. When patients are thin or younger, the relative absence of fat can make the appendix and surrounding fat stranding difficult to see.<ref name="plumpy1"/>

====Magnetic resonance imaging====
[[Magnetic resonance imaging]] (MRI) use has become increasingly common for diagnosis of appendicitis in children and pregnant patients due to the radiation dosage that, while of nearly negligible risk in healthy adults, can be harmful to children or the developing baby.<ref>{{Cite journal |last1=D'Souza |first1=Nigel |last2=Hicks |first2=Georgina |last3=Beable |first3=Richard |last4=Higginson |first4=Antony |last5=Rud |first5=Bo |date=2021-12-14 |editor-last=Cochrane Colorectal Group |title=Magnetic resonance imaging (MRI) for diagnosis of acute appendicitis |journal=Cochrane Database of Systematic Reviews |language=en |volume=2021 |issue=12 |pages=CD012028 |doi=10.1002/14651858.CD012028.pub2 |pmc=8670723 |pmid=34905621}}</ref> In pregnancy, it is more useful during the second and third trimester, particularly as the enlargening uterus displaces the appendix, making it difficult to find by ultrasound. The periappendiceal stranding that is reflected on CT by fat stranding on MRI appears as an increased fluid signal on T2 weighted sequences. First-trimester pregnancies are usually not candidates for MRI, as the fetus is still undergoing [[organogenesis]], and there are no long-term studies to date regarding its potential risks or side effects.<ref>{{cite journal | vauthors = Burke LM, Bashir MR, Miller FH, Siegelman ES, Brown M, Alobaidy M, Jaffe TA, Hussain SM, Palmer SL, Garon BL, Oto A, Reinhold C, Ascher SM, Demulder DK, Thomas S, Best S, Borer J, Zhao K, Pinel-Giroux F, De Oliveira I, Resende D, Semelka RC | title = Magnetic resonance imaging of acute appendicitis in pregnancy: a 5-year multi-institutional study | journal = American Journal of Obstetrics and Gynecology | volume = 213 | issue = 5 | pages = 693.e1–6 | date = November 2015 | pmid = 26215327 | doi = 10.1016/j.ajog.2015.07.026 }}</ref>

====X-ray====
[[File:AppendicolithPlainXray.png|thumb|Appendicolith as seen on plain X-ray]]
In general, plain abdominal radiography (PAR) is not useful in making the diagnosis of appendicitis and should not be routinely obtained from a person being evaluated for appendicitis.<ref>{{cite journal | vauthors = Rao PM, Rhea JT, Rao JA, Conn AK | title = Plain abdominal radiography in clinically suspected appendicitis: diagnostic yield, resource use, and comparison with CT | journal = The American Journal of Emergency Medicine | volume = 17 | issue = 4 | pages = 325–328 | date = July 1999 | pmid = 10452424 | doi = 10.1016/S0735-6757(99)90077-3 }}</ref><ref>{{cite journal | vauthors = Boleslawski E, Panis Y, Benoist S, Denet C, Mariani P, Valleur P | title = Plain abdominal radiography as a routine procedure for acute abdominal pain of the right lower quadrant: prospective evaluation | journal = World Journal of Surgery | volume = 23 | issue = 3 | pages = 262–264 | date = March 1999 | pmid = 9933697 | doi = 10.1007/pl00013181 | s2cid = 23733164 }}</ref> Plain abdominal films may be useful for the detection of [[ureter]]al [[calculus (medicine)|calculi]], [[small bowel obstruction]], or [[perforated ulcer]], but these conditions are rarely confused with appendicitis.<ref name=Sabiston>[http://www.uptomed.ir/Digimed.ir/sabiston-2009/Sabiston_2009/HTML/473.htm APPENDICITIS from Townsend: Sabiston Textbook of Surgery on MD Consult<!-- Bot generated title -->] {{webarchive |url=https://web.archive.org/web/20131203014844/http://www.uptomed.ir/Digimed.ir/sabiston-2009/Sabiston_2009/HTML/473.htm |date=December 3, 2013 }}</ref> An opaque [[fecalith]] can be identified in the right lower quadrant in fewer than 5% of people being evaluated for appendicitis.<ref name=CDEM/> A [[barium enema]] has proven to be a poor diagnostic tool for appendicitis. While failure of the appendix to fill during a barium enema has been associated with appendicitis, up to 20% of normal appendices do not fill.<ref name=Sabiston/>

===Scoring systems===
Several scoring systems have been developed to try to identify people who are likely to have appendicitis.<ref>{{Cite journal |last1=Bahta |first1=Nadir Noureldin Abdella |last2=Rosenberg |first2=Jacob |last3=Fonnes |first3=Siv |date=May 2023 |title=Many diagnostic tools for appendicitis: a scoping review |url=https://pubmed.ncbi.nlm.nih.gov/36735050 |journal=Surgical Endoscopy |volume=37 |issue=5 |pages=3419–3429 |doi=10.1007/s00464-023-09890-2 |issn=1432-2218 |pmid=36735050}}</ref> The performance of scores such as the [[Alvarado score]] and the Pediatric Appendicitis Score, however, are variable.<ref name=Kul2013>{{cite journal | vauthors = Kulik DM, Uleryk EM, Maguire JL | title = Does this child have appendicitis? A systematic review of clinical prediction rules for children with acute abdominal pain | journal = Journal of Clinical Epidemiology | volume = 66 | issue = 1 | pages = 95–104 | date = January 2013 | pmid = 23177898 | doi = 10.1016/j.jclinepi.2012.09.004 }}</ref>

The Alvarado score is the most known scoring system. A score below 5 suggests against a diagnosis of appendicitis, whereas a score of 7 or more is predictive of acute appendicitis. In a person with an equivocal score of 5 or 6, a CT scan or ultrasound exam may be used to reduce the rate of negative appendectomy.

{| class="wikitable" style="margin-left:15px; text-align:center"
|+ Alvarado score
|-
| Migratory right [[iliac fossa]] pain
| 1 point
|-
| [[Anorexia (symptom)|Anorexia]]
| 1 point
|-
| [[Nausea]] and [[vomiting]]
| 1 point
|-
|Right iliac fossa [[tenderness (medicine)|tenderness]]
|2 points
|-
|[[Blumberg's sign|Rebound abdominal tenderness]]
|1 point
|-
|[[Fever]]
|1 point
|-
| High white blood cell count ([[leukocytosis]])
|2 points
|-
|Shift to left (segmented [[neutrophils]])
|1 point
|-
!Total score
!10 points
|}

===Pathology===
Even for clinically certain appendicitis, routine [[histopathology]] examination of appendectomy specimens is of value for identifying unsuspected pathologies requiring further postoperative management.<ref name="Abd Al-Fatah2017">{{cite journal|last1=Abd Al-Fatah|first1=Mohamed|title=Importance of histopathological evaluation of appendectomy specimens|journal=Al-Azhar Assiut Medical Journal|volume=15|issue=2|year=2017|pages=97|issn=1687-1693|doi=10.4103/AZMJ.AZMJ_19_17|s2cid=202550141|doi-access=free}}</ref> No sign of appendicitis in specimens, negative appendectomy, varies but has been estimated to occur in 13% of specimens.<ref>{{Cite journal |last1=Henriksen |first1=Siri R. |last2=Christophersen |first2=Camilla |last3=Rosenberg |first3=Jacob |last4=Fonnes |first4=Siv |date=2023-05-23 |title=Varying negative appendectomy rates after laparoscopic appendectomy: a systematic review and meta-analysis |url=https://link.springer.com/10.1007/s00423-023-02935-z |journal=Langenbeck's Archives of Surgery |language=en |volume=408 |issue=1 |page=205 |doi=10.1007/s00423-023-02935-z |pmid=37219616 |issn=1435-2451}}</ref> Notably, [[appendix cancer]] is found incidentally in about 1% of appendectomy specimens.<ref name="LeeChoi2011">{{cite journal|last1=Lee|first1=Won-Suk|last2=Choi|first2=Sang Tae|last3=Lee|first3=Jung Nam|last4=Kim|first4=Keon Kug|last5=Park|first5=Yeon Ho|last6=Baek|first6=Jeong Heum|title=A retrospective clinicopathological analysis of appendiceal tumors from 3,744 appendectomies: a single-institution study|journal=International Journal of Colorectal Disease|volume=26|issue=5|year=2011|pages=617–621|issn=0179-1958|doi=10.1007/s00384-010-1124-1|pmid=21234578|s2cid=12566272}}</ref><ref>{{Cite journal |last1=Henriksen |first1=Siri Rønholdt |last2=Rosenberg |first2=Jacob |last3=Fonnes |first3=Siv |date=2023 |title=Other Pathologies Were Rarely Reported after Laparoscopic Surgery for Suspected Appendicitis: A Systematic Review and Meta-Analysis |url=https://karger.com/DSU/article/doi/10.1159/000531283 |journal=Digestive Surgery |language=en |volume=40 |issue=3–4 |pages=91–99 |doi=10.1159/000531283 |pmid=37463567 |issn=0253-4886}}</ref>

Pathology diagnosis of appendicitis can be made by detecting a [[neutrophil]]ic infiltrate of the [[muscularis propria]].

Periappendicitis (inflammation of tissues around the appendix) is often found in conjunction with other abdominal pathology.<ref name=pmid2349982>{{cite journal | vauthors = Fink AS, Kosakowski CA, Hiatt JR, Cochran AJ | title = Periappendicitis is a significant clinical finding | journal = American Journal of Surgery | volume = 159 | issue = 6 | pages = 564–568 | date = June 1990 | pmid = 2349982 | doi = 10.1016/S0002-9610(06)80067-X }}</ref>

<gallery>
File:Appendicitis - low mag.jpg|[[Micrograph]] of appendicitis and periappendicitis. [[H&E stain]]
File:Acute appendicitis High Power.jpg|Micrograph of appendicitis showing neutrophils in the muscularis propria. H&E stain
File:Acute suppurative appendicitis with perforation.jpg|Acute suppurative appendicitis with perforation (at right). H&E stain
</gallery>

{|class=wikitable
|+ Classification of acute appendicitis based on [[gross pathology]] and [[light microscopy]] characteristics<ref name="Carr2000">{{cite journal|last1=Carr|first1=Norman J.|title=The pathology of acute appendicitis|journal=Annals of Diagnostic Pathology|volume=4|issue=1|year=2000|pages=46–58|issn=1092-9134|doi=10.1016/S1092-9134(00)90011-X|pmid=10684382}}</ref>
|-
! Pattern !! Gross pathology !! Light microscopy !! Image !! Clinical significance
|-
! Acute intraluminal inflammation
| None visible ||
* Only neutrophils in the lumen
* No ulceration or transmural inflammation
| [[File:Histopathology of acute intraluminal inflammation of the appendix.jpg|190px]]
| Probably none
|-
! Acuta mucosal inflammation
| None visible ||
* Neutrophils within the mucosa, and possibly in the submucosa
* Mucosal ulceration
|
| May be secondary to [[enteritis]].
|-
! Suppurative acute appendicitis
| May be inapparent.
* Dull mucosa
* Congested surface vessels
* Fibropurulent serosal exudate in late cases
* Dilated appendix
|
* Neutrophils in the mucosa, submucosa, and muscularis propria, potentially transmural.
* Extensive inflammation
* Commonly intramural abscesses
* Possibly vascular thrombosis
| [[File:Acute suppurative appendicitis with perforation.jpg|190px]]
| Can be presumed to be the primary cause of symptoms
|-
! Gangrenous/necrotizing appendicitis
|
* Friable wall
* Purple, green, or black color
|
* Transmural inflammation, obliterating normal histological structures
* Necrotic areas
* Extensive mucosal ulceration
| [[File:Histopathology of necrotizing appendicitis, high magnification.jpg|190px]]
| Will perforate if untreated
|-
! Periappendicitis
| May be inapparent.
* Serosa may be congested, dull, and exudative
|
* Serosal and subserosal inflammation, no further than outer muscularis propria to be called isolated
| [[File:Histopathology of periappendicitis.jpg|190px]]
| If isolated, probably secondary to other disease
|-
! Eosinophilic appendicitis
| None visible
|
* >10 eosinophils/mm<sup>2</sup> in muscularis propria.
* No changes conforming to other types of appendicitis
|
| Possibly parasitic, or eosinophilic enteritis.
|}

===Differential diagnosis===
[[File:Enlarged gallbladder with gallstone and cholecystitis.jpg|thumb|[[Coronal plane|Coronal]] [[CT scan]] of a person initially suspected of having appendicitis because of right-sided pain. The CT shows in fact an enlarged [[cholecystitis|inflamed gallbladder]] that reaches the right lower part of the abdomen.]]
Children: [[Gastroenteritis]], [[mesenteric adenitis]], [[Meckel's diverticulum|Meckel's diverticulitis]], [[intussusception (medical disorder)|intussusception]], [[Henoch–Schönlein purpura]], lobar [[pneumonia]], [[urinary tract infection]] (abdominal pain in the absence of other symptoms can occur in children with UTI), new-onset [[Crohn's disease]] or [[ulcerative colitis]], [[pancreatitis]], and abdominal trauma from [[child abuse]]; [[distal intestinal obstruction syndrome]] in children with cystic fibrosis; [[typhlitis]] in children with leukemia.

Women: A pregnancy test is important for all women of childbearing age since an [[ectopic pregnancy]] can have signs and symptoms similar to those of appendicitis. Other obstetrical/ gynecological causes of similar abdominal pain in women include [[pelvic inflammatory disease]], [[ovarian torsion]], [[menarche]], dysmenorrhea, [[endometriosis]], and [[Mittelschmerz]] (the passing of an egg in the ovaries approximately two weeks before menstruation).<ref>{{cite web | title = Pelvic inflammatory disease (PID) Symptoms; Diseases and Conditions | publisher = Mayo Clinic | url = http://www.mayoclinic.org/diseases-conditions/pelvic-inflammatory-disease/basics/symptoms/con-20022341 | access-date = 2015-04-23 | url-status = live | archive-url = https://web.archive.org/web/20150507162533/http://www.mayoclinic.org/diseases-conditions/pelvic-inflammatory-disease/basics/symptoms/con-20022341 | archive-date = 2015-05-07 }}</ref>

Men: [[testicular torsion]]

Adults: new-onset [[Crohn disease]], [[ulcerative colitis]], regional enteritis, [[cholecystitis]], [[renal colic]], perforated [[peptic ulcer]], [[pancreatitis]], [[rectus sheath hematoma]] and [[epiploic appendagitis]].

Elderly: [[diverticulitis]], intestinal obstruction, [[colon cancer|colonic carcinoma]], [[mesenteric ischemia]], leaking [[aortic aneurysm]].

The term "{{visible anchor|pseudoappendicitis}}" is used to describe a condition mimicking appendicitis.<ref name="pmid20633930">{{cite journal | vauthors = Cunha BA, Pherez FM, Durie N | title = Swine influenza (H1N1) and acute appendicitis | journal = Heart & Lung | volume = 39 | issue = 6 | pages = 544–546 | date = July 2010 | pmid = 20633930 | doi = 10.1016/j.hrtlng.2010.04.004 }}</ref> It can be associated with ''[[Yersinia enterocolitica]]''.<ref name="pmid18575909">{{cite book |title=Yersinia enterocolitica infection in diarrheal patients |journal=Eur. J. Clin. Microbiol. Infect. Dis. |volume=27 |issue=8 |pages=741–752 |date=August 2008 |isbn=978-0-9600805-6-4 |pmid=18575909 |doi=10.1007/s10096-008-0562-y |vauthors=Zheng H, Sun Y, Lin S, Mao Z, Jiang B |s2cid=23127869 }}</ref>