Appendicitis is the most common cause of abdominal pain requiring surgical intervention. The lifetime risk of appendicitis is approximately 7%, with a current incidence of 86 per 100,000 patients per year.¹ Rates of appendicitis are highest in the second decade of life, with a slightly higher incidence of appendicitis occurring in males (ratio 1.4:1).² Appendiceal perforation rates also vary; patients at extremes of age are more likely to have perforated at their time of diagnosis.¹ Early diagnosis of appendicitis is paramount, because patient morbidity is increased once appendicitis becomes complicated by abscess and perforation.

The appendix is located on the posteromedial surface of the cecum, approximately 3 cm from the ileocecal valve. Its length varies from 8 to 13 cm, and its anatomic location within the abdomen is variable.³ Although the appendix has no known function, recent studies propose that it acts as a reservoir for commensal bacteria in the colon.⁴

Appendicitis occurs when the appendiceal lumen becomes obstructed by fecaliths, adhesions, enlarged lymph nodes, foreign bodies, parasites, or, less commonly, tumors.^5,6 Once obstruction occurs, the intraluminal pressure within the appendix begins to increase as mucosal secretions accumulate, leading to appendiceal distension. This distension in turn stimulates visceral afferent nerves that enter the spinal cord at the T8 to T10 level, causing dull epigastric or periumbilical pain. As obstruction continues, pressures within the appendix impede venous and lymphatic drainage, allowing bacteria and neutrophils to invade the walls of the appendix. More localized pain occurs after continued inflammation within the appendiceal serosa causes irritation of local somatic fibers on the parietal peritoneum. If this process remains unchecked, the appendix becomes gangrenous and is at risk for perforation, abscess formation, and peritonitis, often within 24 to 36 hours of symptom onset.⁷

Classically, a patient with appendicitis presents with constant pain that is poorly localized to the periumbilical or epigastric region, and is accompanied by anorexia, nausea, and vomiting. Vomiting usually begins after the abdominal pain. Illness progression leads to migration of pain to the right lower quadrant at the area of the McBurney point, and can be accompanied by low-grade fever. A meta-analysis evaluating patients with abdominal pain reported an increased likelihood of appendicitis when the patient’s pain was located in the right lower quadrant, had migrated from the periumbilical region, and had been accompanied by fever.⁸

However, this classic clinical presentation is not always present, partly because of the variability of the appendiceal location within the abdomen. For example, the appendix may lie in a retrocecal, retroiliac, or pelvic location, leading to pain in the right flank, pelvis, testicle, suprapubic region, or even left lower quadrant if the appendix crosses the midline. Likewise, patients may experience dysuria, urinary frequency, diarrhea, or tenesmus depending on the location of the inflamed appendix. These varied positions of the appendix and their associated complaints can delay the early diagnosis of appendicitis and increase the risk of gangrene and perforation.⁹

Multiple physical examination findings exist to aid in the diagnosis of appendicitis. Pain with palpation is classically found at the McBurney point, located “exactly between an inch and a half and two inches from the anterior spinous process of the ileum on a straight line drawn from that process to the umbilicus.”¹⁰ A positive Rovsing sign is present when palpation of the left lower quadrant elicits tenderness in the right lower quadrant. Patients may also show rebound tenderness or guarding, which are responses to the inflamed parietal peritoneum, and, when present, have been found to be independent predictors of appendicitis.¹¹

Additional signs can aid in the physical diagnosis. The psoas sign is performed either by having the patient flex at the right hip against resistance, or by extending the hip with the patient in the left lateral decubitus position, thereby irritating the iliopsoas muscle. A positive obturator sign is present when internal rotation of the flexed right hip with the knee in flexion exacerbates the patient’s pain. A rectal examination is often performed, although the sensitivity and specificity of rectal tenderness for appendicitis are weak.⁸

Temperature is either normal or slightly increased early in the course of appendicitis. Patients may develop fever as the disease state progresses toward perforation and abscess formation. Therefore, temperature increase alone cannot rule in the diagnosis of appendicitis, but the presence of a fever, when taken in concert with other history and physical examination findings, such as migration of pain, can make the diagnosis more likely.⁸

Appendicitis should be considered in the differential diagnosis for all patients presenting with epigastric, periumbilical, or right-sided abdominal or flank pain. Although no single test is specific for appendicitis, some laboratory data may aid in the diagnosis. A urinary pregnancy test should be performed in all women of childbearing age, and pelvic examination should be performed in addition to the abdominal examination. Some women may have adnexal tenderness with inflamed pelvic appendices. A urinalysis should be performed as well, although it is important to keep in mind that hematuria or pyuria can be present in appendicitis if the inflamed appendix is in close proximity to the bladder or ureter.

Ultrasound

Ultrasound can be a useful test in the evaluation of appendicitis, particularly in children and pregnant women in whom there are particular concerns regarding ionizing radiation. The sensitivity of graded compression ultrasonography is as high as 98% (although these numbers vary widely between studies)³¹ and is considered positive for appendicitis when the diameter of the appendix is greater than 6 to 7 mm (Fig. 1).^27,32,33 Inflammation surrounding the appendix, appendicoliths, or hyperemia of the appendiceal wall can also be visualized by ultrasound in the setting of acute appendicitis. False negatives can occur once the appendix has perforated, thus reducing the diameter of the appendix, or when the appendix is retrocecal or inflammation is confined to the tip of the appendix.³⁴ Another challenge in using ultrasound is that the appendix cannot always be visualized. Even using skilled sonographers, the appendix is not visualized between 25% and 35% of the time,^27,33 which can be partly caused by patient’s body habitus or bowel gas overlying the appendix. The negative predictive value of a nonvisualized appendix on ultrasound is 90%.²⁷ Thus, although a positive ultrasound is diagnostic of appendicitis, a negative ultrasound in which the appendix is not seen cannot rule out the diagnosis of acute appendicitis, and other diagnostic tools should be used.

Fig. 1 Ultrasound shows an enlarged appendix with a fluid-filled lumen.

(From Paterson A, Sweeney LE, Connoly B. Paediatric abdominal imaging. In: Grainger R, Allison D, eds. Grainger & Allison’s Diagnostic Radiology: A Textbook of Medical Imaging. 5th Edition. Philadelphia: Churchill Livingston, 2008; with permission.)

CT

CT has become widely used in the evaluation of suspected appendicitis. Advantages include its widespread availability as well as its capacity to detect other abdominal disorders. Disadvantages include patient radiation exposure, time delay to diagnosis if oral contrast is used, and risk of contrast-induced nephropathy or contrast reaction when intravenous contrast is used. Some investigators consider increased cost to be a disadvantage of this imaging modality, but data have suggested a decrease in the rates of unnecessary appendectomy since CT scan use has increased.³⁵ Findings suggestive of acute appendicitis on CT scan include an enlarged appendix with diameter greater than 6 mm, appendiceal wall thickening, and pericecal inflammation (Fig. 2). An appendicolith alone is not sufficient to make a radiographic diagnosis of appendicitis.³⁶

Fig. 2 Appendicitis. A CT scan shows an edematous appendix with a diameter greater than 1 cm (arrow), consistent with acute, uncomplicated appendicitis.

(From Prather C. Inflammatory and anatomic diseases of the intestine, peritoneum, mesentery, and omentum. In: Goldman L, Ausiello DA, eds. Cecil medicine. 23rd edition. Philadelphia: Saunders, 2007; with permission.)

Some controversy exists about the use of contrast in the evaluation of appendicitis on CT. The sensitivity (83%–97%) and specificity (93%–98%) of CT in acute appendicitis vary with the presence or absence of contrast, as well as type of contrast used. A recent review article found the sensitivity and negative predictive value of CT without oral contrast to be equal to that of CT with oral contrast; the specificity, accuracy, and positive predictive value of CT without oral contrast was superior to that of CT with oral contrast in this analysis.³⁷ The implication of this review may have important ramifications on emergency department (ED) length of stay and may decrease time until surgical intervention for patients. Other studies have shown the sensitivity of noncontrast scans to be greatly inferior to those using contrast.³⁸

Another promising option uses rectal contrast only. In a series of 100 patients, CT with rectal contrast had a sensitivity, specificity, positive and negative predictive values, and accuracy of 98% in diagnosing acute appendicitis.³⁹ More recent prospective data have shown more modest outcomes for this modality, but imply that rectal contrast studies can be useful in the evaluation of acute appendicitis.³⁸ Perhaps the best approach to the use of contrast in patients suspected of having appendicitis should take into account the breadth of the differential diagnosis. Oral and intravenous contrast may help better delineate other causes of abdominal pain (particularly in young women) and should be considered when the diagnosis of appendicitis is uncertain. Establishing an institutional protocol with respect to contrast administration may also aid in the decision of whether contrast should be used, and by what route.

Patients with appendicitis should receive intravenous hydration, symptomatic relief, and antibiotics. Electrolyte imbalances should be corrected and crystalloids administered for patients with dehydration or sepsis. Antiemetics should be considered in patients with vomiting. Narcotic pain medication can be administered to maximize patient comfort.

A recent review article confirms that antibiotics can prevent postoperative wound infection in uncomplicated appendicitis and minimize abscess formation in cases of perforation.⁴³ Antibiotic therapy should include coverage for enteric gram-negative organisms as well as anaerobes, and should be considered in conjunction with the consulting surgeon. Possible regimens include a second- generation or third-generation cephalosporin for uncomplicated cases. In the event of abscess formation or perforation, broader-spectrum coverage with a medication such as piperacillin-tazobactam or a 3-drug regimen including a cephalosporin and aminoglycoside along with metronidazole is warranted.⁴⁴

A study investigating antibiotic and medical management versus appendectomy showed that, although most patients improved in the short term with medical management, greater than one-third of patients required surgery for recurrent appendicitis within a year.⁴⁵ Therefore, operative intervention remains the definitive treatment of acute appendicitis, and early surgical consultation is necessary. In cases of abscess formation at time of presentation, surgeons may opt for initial percutaneous abscess drainage initially, followed by interval appendectomy.

Diverticular disease is commonly seen in the adult population. The overall prevalence of diverticulosis has been reported to be roughly 27% and increases with advancing age.⁴⁶ Of those patients with symptoms from diverticular disease, 3% are less than 40 years of age, whereas each decade between the ages of 50 and 70 years accounts for approximately 25% to 30% of cases.⁴⁷ The prevalence is much higher in developed countries, and is believed to be partly the result of physical inactivity⁴⁸ and a low-fiber diet.⁴⁹ Symptomatic disease, including diverticular pain and diverticulitis, occurs in roughly 10% to 25% of patients with diverticulosis.⁵⁰

Diverticula are small outpouchings or herniations that form at areas of weakness in the wall of the colon. In general, they are located at the vulnerable areas in which the vasa recta enters the muscularis. Except for diverticula of the cecum, which comprise all 3 layers of the colonic wall, most acquired diverticula contain mucosa and submucosa only. Diverticular disease affects the left-sided and sigmoid colon more than 90% of the time.⁵¹ Although many causes of diverticulosis have been proposed, the exact cause of the condition is not known. Problems of colonic motility and muscular abnormalities of the colon wall are possible causes. Another hypothesis is that diverticulosis is a disorder arising from increased intraluminal pressure.⁵² Although diverticulosis is largely an asymptomatic condition, these areas can perforate and become inflamed, leading to diverticulitis.

Patients can have either complicated or uncomplicated episodes of diverticulitis, which has ramifications for treatment as well as patient morbidity. Complicated cases are those in which there is perforation, obstruction, abscess, or fistula formation.⁵³

Patients with diverticulitis typically present with constant left lower quadrant or suprapubic pain. Patients may also complain of fever, malaise, constipation, diarrhea, tenesmus, and urinary symptoms if the bladder becomes irritated by the inflamed colon. On examination, patients typically have left lower-quadrant tenderness, which may be accompanied by localized guarding or rebound. At times, a palpable abdominal mass caused by an underlying abscess may be appreciated.

Patients with acute diverticulitis may also present with right-sided abdominal symptoms. This possibility applies particularly to Asian⁵⁴ and younger⁵⁵ patients, who are more likely to have proximal colonic disease. In addition, redundant sigmoid colon may be present on the right side of the abdomen, leading to right-sided symptoms in patients with distal colonic disease.

A high index of suspicion is necessary when evaluating patients who are elderly or immunocompromised. These groups may present with less-impressive symptoms and physical examination findings. As a result, they are more likely to have perforation at the time of diagnosis.^56,57

Patients may also complain of symptoms related to fistula formation, which may occur between the bowel and bladder, leading to pneumaturia or fecaluria, or between the bowel and vagina, with women complaining of a feculent vaginal discharge. In addition, enterocolonic fistulas may occur and lead to copious diarrhea.

Patients with acute diverticulitis often have an increased WBC count and may also have a leftward shift. Other laboratory abnormalities may be present in patients with vomiting and diarrhea or in those with more advanced septicemia.

Imaging options are available when the diagnosis of diverticulitis is uncertain, or if suspicion exists for complications of diverticular disease. Contrast enema has typically been considered the gold standard in diagnosis, although it is falling out of favor as a first-line study. Although contrast enema is able to diagnose diverticulitis, it is unable to assess for the presence of an abscess and cannot determine the severity of inflammation.⁵⁸ Thickened colonic folds, contrast extravasation, and localized mass effect may be seen on contrast radiography.⁵⁹ Fistula formation may also be evident. The use of non–water-soluble contrast material in colonic contrast studies can also lead to problems associated with intraperitoneal barium when perforation is present, and should therefore be avoided in patients with signs of local peritonitis on examination. If this type of imaging is used, it is best to use water-soluble contrast.

CT is the study most used for the diagnosis of diverticulitis. CT with both oral and intravenous contrast has the advantage of being able to evaluate the colonic walls as well as extraluminal areas, in addition to being able to assess for other causes of abdominal pain. The sensitivity of CT for diagnosis of diverticulitis ranges from 85% to 97%.⁶⁰ Positive findings of diverticulitis include thickening of the bowel wall and fascia, pericolic fat stranding, and local abscess formation (Fig. 3).⁶¹

Fig. 3 CT scan of a patient with acute diverticulitis showing colon wall thickening, a mass adjacent to the sigmoid, and stranding of the fat.

(From Brandt LJ, Feuerstat P. Intestinal ischemia. In: Feldman M, Friedman LS, Brandt LJ, eds. Sleisenger & Fordtran’s gastrointestinal and liver disease. 8th edition. Philadelphia: Saunders, 2010; with permission.)

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