The Case (http://www.medscape.com/viewprogram/15726_pnt): A 60-year-old man presents to the emergency department (ED) complaining of a 1-day history of crampy, moderately intense, left-sided abdominal pain. The pain is constant in nature and exacerbated by movement; it is relieved by lying still. The patient has not experienced anorexia and has not eaten since the evening before. He has had several loose brown stools but denies any nausea or vomiting. The stool in his bowel movements is not blood streaked and does not appear tarry. He denies any recent travel or camping and has not eaten any uncooked or undercooked foods. He reports feeling febrile, sweaty, and generally fatigued. No urinary symptoms, such as dysuria or increased frequency, are reported. He has not had any recent contact with sick people. He denies having had similar episodes in the past. His medical and surgical histories are unremarkable, although he did have a screening barium enema examination 3 years ago. He is a nonsmoker and denies any heavy or regular alcohol consumption. He does not take any prescription or over-the-counter medications.

On physical examination, the patient has an elevated temperature of 101.3ºF (38.5ºC), a blood pressure of 130/76 mm Hg, a pulse of 110 bpm, and a respiratory rate of 20 breaths/min. The patient is not in acute distress, but he is mildly ill-appearing and diaphoretic. His oropharynx is clear, with slightly dry mucous membranes. His lungs are clear to auscultation, and his heart rate is regular, without murmurs. The abdominal examination reveals moderate tenderness in the left lower quadrant, with voluntary guarding. There is no rebound tenderness. No costovertebral angle tenderness or inguinal hernias are appreciated, and his genital exam is noted to be normal. On digital rectal examination, the patient is tender on the left side of the rectal vault, and the stool is noted to guaiac-negative. The remainder of the physical examination is unremarkable.

Serum laboratory testing is remarkable only for an elevated white blood cell (WBC) count of 16.0 × 10³/µL (16.0 × 10⁹/L), with a neutrophil predominance; the urinalysis is unremarkable. A standard radiograph of the abdomen is obtained, which does not show any significant abnormalities. The patient then undergoes a computed tomography (CT) scan of the abdomen and pelvis.

DIAGNOSIS:

Acute diverticulitis results from inflammation of a diverticulum (small mucosal and submucosal herniations through the circular muscle layer of the colonic wall) secondary to fecal obstruction. The obstruction typically occurs at the neck of the diverticulum; solidified stool, which typically forms a fecalith, abrades the mucosa within or at the neck of the diverticulum. In uncomplicated cases (typically characterized by a well-appearing patient without peritonitis and systemic signs/symptoms), the inflammatory process is confined to the colonic wall; however, the obstruction, with subsequent high intraluminal pressure within the diverticula, can lead to a microperforation which, in turn, allows translocation of bacteria through the colonic wall, pericolic abscess formation, and diffuse peritonitis. Only 2-4% of patients diagnosed with diverticulitis are younger than 40 years old; the condition is predominantly found in elderly populations.^[1,2]

The colonic diverticula themselves are most commonly found in the sigmoid and descending colon, although, less commonly, patients develop diverticula of the right colon (particularly in patients of Asian descent). The condition of diverticulosis is an intestinal disorder that is characterized by the presence of many diverticula and which occurs equally in men and women, with a higher prevalence in cultures with a low-fiber diet (a low-fiber diet is believed to decrease stool transit time, thereby causing increased intraluminal pressure and resulting in mucosal herniations). Approximately one third of the population has diverticulosis by age 50 years, and about two thirds have it by age 85 years. Approximately 10-25% of patients with known diverticulosis go on to develop diverticulitis.^[1,2]

The classic presentation of diverticulitis consists of steady, deep abdominal pain that is often initially diffuse and vague, but later localizes in the left lower quadrant of the abdomen. Abdominal bloating, stool changes such as diarrhea or constipation, and flatulence frequently accompany acute diverticulitis. Fevers, fatigue, and anorexia are also common complaints. Colonic inflammation may irritate the bladder or the ureters, leading to complaints of urinary frequency and dysuria. A physical examination may reveal fever; localized, left lower quadrant abdominal tenderness; mild abdominal distention; and, at times, a left lower quadrant mass. The palpated mass is likely to be inflamed loops of bowel or, possibly, an abscess. A digital rectal examination may demonstrate left-sided tenderness and occult blood in the stool.^[1,2]

The differential diagnosis of acute sigmoid diverticulitis is broad and includes inflammatory bowel disease, irritable bowel syndrome, appendicitis, ischemic colitis, colon cancer, urolithiasis, urinary tract infection, and, in women, a number of obstetric/gynecologic conditions (such as tubo-ovarian abscesses and ovarian cysts). The complications of acute diverticulitis include the formation of a pericolic abscess, frank colonic perforation leading to free intra-abdominal air, local adhesions, purulent or fecal peritonitis, sepsis, bowel obstruction, and fistula formation between the colon and the bladder or vagina. Fistula formation is more common in the setting of recurrent diverticulitis, with the most common type being a colovesicular fistula that is characterized by fecaluria, pneumaturia, or typical urinary tract infection symptoms.^[1,2]

The initial evaluation of a patient with suspected acute diverticulitis generally includes a physical examination, complete blood cell count, urinalysis, and, when indicated by the presence of peritonitis, plain x-rays of the abdomen to rule out colonic perforation. Plain films are of limited value; however, they may show colonic obstruction, mild ileus, or bowel distention. Leukocytosis is found in only 36% of cases of acute diverticulitis. The preferred imaging modality for the diagnosis of acute diverticulitis is CT scanning, as it detects both the extent of the disease and the presence of complications. Abdominal ultrasonography can also be used, but it lacks specificity and is operator-dependent. Barium contrast studies and colonoscopy/sigmoidoscopy should be avoided in the setting of acute diverticulitis because of the risk of bowel perforation; however, these examinations are often performed after resolution of the acute stage in order to evaluate for the presence of complications, such as fistula formation or other colonic abnormalities.^[1,2]

The management of patients with acute diverticulitis depends upon the severity of the illness, but it is most commonly successful with medical management alone. Well-appearing patients who are able to tolerate oral intake and who do not have systemic symptoms, peritonitis, or complications seen on CT scans may be treated as outpatients. In fact, reliable, nontoxic-appearing patients with a history of diverticulitis who present with their typical symptoms may even be treated empirically as outpatients, without repeat imaging, if no significant comorbidities (eg, an immunocompromised state, diabetes, or malignancy) exist. All patients treated at home require close follow-up care and reexamination, and they should be given detailed return precautions for worsening pain or systemic illness. Treatment of uncomplicated acute diverticulitis consists of bowel rest, broad-spectrum antibiotics, and pain control. Outpatients may be instructed to begin with a clear liquid diet and advance slowly as tolerated, whereas inpatients should be kept hydrated with intravenous fluids. Antibiotic regimens should cover gram-negative bacteria and anaerobes. A combination of either trimethoprim-sulfamethoxazole or ciprofloxacin, with either metronidazole or clindamycin, is the primary recommended treatment regimens. Monotherapy with amoxicillin/clavulanic acid is an acceptable alternative regimen.^[1,2]

Patients should be admitted to the hospital if they cannot tolerate oral intake of fluids, are immunocompromised, demonstrate signs of systemic toxicity (such as tachycardia and fever), or have developed evidence of peritonitis or intra-abdominal complications. These patients should receive nothing by mouth (NPO) and should be given intravenous antibiotics. Ciprofloxacin or an aminoglycoside may be paired with metronidazole or clindamycin as the recommended antibiotic regimen. A monotherapeutic agent, such as piperacillin/tazobactam, ampicillin/sulbactam, or ertapenem, may also be used.^[1]

Selected abscesses detected by ultrasonography or abdominal CT scanning may be drained percutaneously, whereas perforations, fecal peritonitis, and fistula formation all require a surgical consultation. Abscesses less than 5 cm in diameter can be treated with antibiotics alone, although evaluation by a surgeon should still be sought. Recurrent diverticulitis and complicated diverticulitis are indications for partial colonic resection. Approximately 10-25% of patients who are medically managed have recurrent attacks and are at an increased risk of subsequent complication. Interestingly, patients younger than age 40 years are more likely to suffer from recurrences and are more likely to benefit from elective sigmoid resection.^[1,2]

In this case, the axial CT scan images of the abdomen at the level of the pelvis (see Figures 2 and 3) show acute diverticulitis of the sigmoid colon, with multiple diverticula (arrow heads), wall thickening (arrow in Figure 3), and inflammatory stranding in the sigmoid mesentery (asterisk in Figure 2). There is no free air or abscess formation. The screening barium enema performed 3 years ago shows multiple diverticula in the sigmoid and descending colon.  As a result of systemic signs and symptoms of infection, this patient was admitted to the hospital. He was placed on bowel rest and started on intravenous metronidazole and ciprofloxacin. Over the next 2 days, the patient defervesced and his leukocytosis resolved. His diet was advanced to a full diet, and he was discharged from the hospital on a 10-day course of amoxicillin/clavulanic acid.

REFERENCES

1. Nguyen MCT, Chudasama YN, Dea SK, Cooperman A. Diverticulitis. eMedicine from WebMD [serial online]. Last updated: June 30, 2008. Available at: www.emedicine.com/MED/topic578.htm. Date accessed: July 17,2008.
2. Janes SEJ, Meagher A, Frizelle FA. Management of diverticulitis. BMJ. 2006;332:271-75. Abstract
3. Joffe S, Kachulis A, Horowitz M. Colon, diverticulitis. eMedicine from WebMD [serial online]. Last updated February 26, 2008. Available at: www.emedicine.com/radio/topic183.htm. Date Accessed: July 17, 2008.
4. Tintinalli JE, Kelen GD, Stapczynski JS. Emergency Medicine: A Comprehensive Study Guide. 6th ed. New York: McGraw-Hill;2004:536-9.