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Acute Diverticulitis
Abstract
Diverticulitis of the colon is an extremely common disease, accounting for close to 30,000 annual hospital admissions in the United States. Asymptomatic diverticulosis is widely pervasive among older individuals of Westernized countries; however, the rate of progression to acute diverticulitis is likely less than 10%. Although the precise pathogenesis of progression from diverticulosis to diverticulitis is not clear, herniation of bowel mucosa through the colon wall results in the clinical manifestation of diverticular disease. The presentation and clinical course can range from mild to severe, including an acute abdomen in cases of free perforation. Computed tomography (CT) is considered the standard diagnostic test, allowing stratification of a clinical presentation into “uncomplicated” or “complicated” categories as well as guiding and informing subsequent treatment decisions. Because diverticulitis represents a wide spectrum of acuity, treatment must be individualized to each patient’s clinical presentation and may consist of antibiotic treatment alone, percutaneous drainage, or possible urgent surgical intervention for source control or sequelae secondary to complications related to diverticular disease (e.g., fistula, obstruction). With better understanding of the disease process and its natural history, the necessity for antibiotics as well as surgical resection has been increasingly studied. Management of patients initially treated without surgery continues to remain an unsettled debate. Currently, the American Society of Colon and Rectal Surgeons (ASCRS) recommends an individualized approach for each patient based on age, comorbidities, frequency and intensity of diverticular episodes.
Clinical Vignette
A 68-year-old woman presented with new-onset pneumaturia and dysuria. She denied associated abdominal pain, fever, or fecaluria. She had experienced two prior episodes of CT–proven uncomplicated diverticulitis managed successfully with antibiotics, each requiring a short hospitalization. These episodes were not associated with a diverticular abscess, and both attacks occurred within the previous 12 months. She had undergone colonoscopy following clinical resolution of her most recent diverticulitis episode, which was notable only for sigmoid diverticulosis. She had a benign abdominal examination eliciting no tenderness to palpation. A urinalysis contained bacteria and leukocyte esterase, consistent with a urinary tract infection. A CT scan of the abdomen and pelvis demonstrated air within the bladder and a redundant sigmoid colon loop with wall thickening opposing the dome of the bladder, consistent with a diverticular colovesical fistula.
COMMENT: In a surgically fit patient, a diverticular colovesical fistula should call for surgery. Colovesical fistula, colovaginal fistula, and diverticular stricture are often secondary sequelae of prior diverticular episodes and are classified as “complicated” diverticulitis.
There are two main types of diverticular disease. True diverticula are congenital, contain all layers of the bowel wall, and are more common in the Eastern Hemisphere. These are not the subject of this review. Acquired (false) diverticula are more common and form when the mucosa and submucosa of the bowel herniate through the muscular layer of the bowel wall. Between the longitudinal muscular layer of the colon (which forms the taenia coli), intrinsic weakness within the colon wall exists where the vasa recta penetrate. These vessels penetrate the mesenteric side of the taenia and continue submucosally and symmetrically around the bowel wall. Diverticular herniation occurs at these weak points due to concomitant localized, elevated sigmoid intraluminal pressure ( Fig. 44.1 ). Although acquired (false) diverticula can affect any segment of the colon, they are, in the industrialized western world, predominantly concentrated in the left side of the colon. The sigmoid colon is disproportionally affected. This is attributed to the higher intraluminal pressure generated within the segment when stool is being propelled antegrade. Diverticula may extend proximally within the colon and rarely throughout the entire colon (pandiverticulosis). However, they do not involve the rectum (no taenia).
Diverticulosis.
Diverticula themselves are asymptomatic but can become symptomatic due to inflammation (diverticulitis) or bleeding. It is difficult to assess the overall prevalence of diverticulosis, but autopsy studies have suggested that the prevalence increases with age, with less than 10% of individuals younger than 40 years of age having diverticula compared with over 80% by age 80. Historically, it has been estimated that 10% to 25% of persons with diverticula progress to acute diverticulitis. However, more contemporary studies suggest that this rate is likely less than 10%. Within this proportion of patients progressing to diverticulitis, 75% of cases are “uncomplicated” and the remaining 25% are “complicated,” associated with free perforation, abscess, obstruction, or fistula.
Several studies have reported a higher incidence of diverticula and diverticular disease in Western countries. Diverticular disease is rare in Asia and Africa, although the incidence appears to be rising as these areas become more industrialized. This finding has supported the hypothesis that environmental factors, specifically diet, may play a key role in development of the disease.
A recent review using the National Hospital Discharge Survey estimated that diverticulitis accounts for 300,000 admissions and 1.5 million days of inpatient care annually in the United States. One study reported that over 50% of all sigmoid resections and over 30% of all colostomies performed in the state of Washington were done for diverticulitis.
Risk Factors and Pathophysiology
The risk of diverticular disease increases with age. The mean age of affected patients is 62 years, with an increasing prevalence among older adults. Because the US population older than 75 years of age is growing rapidly (a 33% increase from 1998 to 2005), this cohort is an important subset who will be encountered with diverticulitis. The male-to-female ratio of prevalence is estimated to be between 2:1 and 3:1. Diverticulitis has been linked with several environmental factors including diet, obesity, and smoking. It is theorized that a low-fiber diet leads to small hard stools that lead to increased intraluminal colonic pressures, muscular hypertrophy, and segmentation of the colon, which leads to radially directed pressure and subsequent perforation. Support for this theory comes from several studies including an autopsy review, which found that Japanese immigrants exposed to a Westernized diet had a 52% incidence of colonic diverticula versus 1% of time-matched native Japanese. Links have been sought between obesity and smoking and diverticular disease, but studies have yielded conflicting results and the confounder of diet complicates interpretation.
Although patients who present with uncomplicated disease as their first episode are unlikely to have another attack (complicated or uncomplicated), patients who are admitted for a recurrence of uncomplicated diverticulitis are at increasing risk of having further recurrent episodes. Patients who have had one episode of diverticulitis are at increased risk for subsequent attacks. A retrospective review of a statewide hospital discharge database showed that 19% of patients who underwent initial nonoperative treatment for diverticulitis had a subsequent admission for a recurrent episode.
Clinical Presentation
Diverticulitis presents with symptoms ranging from mild intermittent abdominal pain to an acute abdomen with peritonitis, sepsis, and multiorgan failure. Suspected acute early or mild diverticulitis (contained microperforation) causes abdominal pain localizing to the left lower quadrant as peritoneal irritation develops. Patients may develop nausea, fever, and malaise. Additional key symptoms to consider are fecaluria, pneumaturia, and vaginal drainage, which may suggest a fistulous communication between the colon and the bladder or vagina (colovesical or colovaginal fistula). Symptoms may be nonspecific, and alternative diagnoses to consider when patients present with suspected diverticulitis include enteritis, irritable bowel syndrome, inflammatory bowel disease, urinary tract infections or obstruction (nephrolithiasis), appendicitis, neoplasia, gynecologic disease, and bowel obstruction ( Fig. 44.2 ). If the inflammatory process extends beyond a contained perforation, the patient usually experiences more severe abdominal pain, nausea, vomiting, ileus, fever, and systemic signs of sepsis. This may progress to generalized peritonitis, resulting in an acute abdomen, which can potentially evolve into multiorgan system failure. Aggressive resuscitation and emergent abdominal exploration for the control of intra-abdominal sepsis are indicated for patients presenting in extremis.
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