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Diverticular disease as its own entity, following a management algorithm that shifted meaningfully in the last decade while the boards catch up. Uncomplicated diverticulitis is now an inflammatory process treated with selective rather than reflex antibiotics, and prophylactic resection by episode count is dead. Complicated disease grades on Hinchey and splits at the four-centimeter abscess threshold.
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Board Pearls is a gastroenterology board review built around clinical reasoning, not recall. Each episode takes one high-yield topic and works it the way you would on rounds: a case to anchor it, the framework that sorts the differential, and the specific decisions the exam rewards.
The gastroenterology series covers the full blueprint across nine modules: esophagus, stomach and duodenum, small bowel, colon, pelvic floor, liver, pancreas and biliary, endoscopy, and the cross-cutting topics. Episodes are grouped by chapter and built from the primary guidelines and pivotal trials the boards draw from (ACG, AGA, AASLD, ASGE), not from textbook summaries.
Use it as an audio companion to the written curriculum, MCQs, and AI tutor at boardpearls.com. Questions or feedback: hello@boardpearls.com.
Welcome to Board Pearls. This is episode two of two of the Colorectal Cancer, Polyps, and Diverticular Disease chapter, in the Colorectal and Pelvic Floor Disorders module. This episode is diverticular disease as its own entity: the biology, uncomplicated diverticulitis where antibiotics are now selective rather than reflex, complicated disease graded by Hinchey, the segmental colitis that mimics IBD, and the elective surgery question.
Diverticular disease is the cancer chapter's quiet companion, with its own biology and a management algorithm that has shifted meaningfully in the last decade, and the shifts matter because the boards are still catching up to clinicians who trained on the old rules: reflex antibiotics for every diverticulitis, and elective resection after a fixed episode count. Both have moved, and the new positions are what the stems test.
Start with the anatomy, because the rest follows from it. Diverticulosis is herniation of colonic mucosa and submucosa through the muscle layer, happening at fixed weak points where the feeding vessels penetrate the muscle, so over decades of intraluminal pressure the mucosa bulges through those points, producing a false diverticulum, a pouch of mucosa and submucosa without a muscular wall. The lesions cluster where the vessels enter, and in Western populations the sigmoid is overwhelmingly the site because it generates the highest pressures, while in Asian populations the right colon is more often involved, which matters in the vignette of a younger Asian patient with right-lower-quadrant pain. Prevalence climbs steeply with age, uncommon in young adults and present in most people by their eighties, so incidental diverticulosis is the single most common colonoscopy finding in older adults, and most of it stays asymptomatic for life, with only a small fraction developing a complication, of which diverticulitis is the most common and bleeding the second.
Acute diverticulitis is inflammation of a diverticulum, classically beginning with microperforation at the apex of an obstructed pouch, with pain in the left lower quadrant for sigmoid disease and the right for right-sided disease, followed by fever and leukocytosis. The diagnosis is confirmed on contrast-enhanced CT, which shows the diverticula, the pericolic fat stranding, and the wall thickening, and grades severity by identifying or excluding the complications that change management, abscess, free perforation, fistula, and obstruction, so CT is both diagnostic and prognostic in one study. The Hinchey classification stages complicated disease: a pericolic phlegmon without a drainable cavity, a discrete pericolic abscess, a pelvic or distant abscess extending beyond the immediate tissue, purulent peritonitis, and feculent peritonitis. That grading isn't academic, because it drives the split between medical management, percutaneous drainage with antibiotics, and surgery.
The biggest change runs through uncomplicated diverticulitis. The old rule gave every patient antibiotics because the disease was framed as bacterial infection of a microperforated pouch, but a randomized trial reframed it: observation and antibiotics gave no difference in recovery, complications, recurrence, or surgery, which implies that uncomplicated diverticulitis in immunocompetent patients behaves more like an inflammatory process than an infectious one, where the bacteria are present but the host response drives the course without antibiotic help. So the current recommendation is that initial management of acute uncomplicated left-sided diverticulitis is supportive care with selective rather than universal antibiotics, and the eligible patient is an immunocompetent outpatient without a systemic inflammatory response, not frail, not needing hospitalization, with adequate follow-up. The favored stem is the well-appearing immunocompetent patient with left-lower-quadrant pain, a low-grade fever, mild leukocytosis, tolerable oral intake, and CT showing uncomplicated sigmoid diverticulitis, where the answer is supportive care without antibiotics and close follow-up, and the wrong move is reflex ciprofloxacin and metronidazole because that was the old rule.
The exceptions matter as much as the principle: antibiotics remain standard for anyone immunocompromised, frail, septic, requiring admission, or with any complicated feature on CT, because the host response that drives spontaneous resolution is exactly what a transplant recipient or a patient on chronic steroids can't mount, and the same excludes the frail elderly patient even when the imaging looks uncomplicated. When antibiotics are indicated, oral regimens like ciprofloxacin plus metronidazole or amoxicillin-clavulanate cover the gram-negative and anaerobic flora, with intravenous regimens for admitted patients.
Complicated diverticulitis adds anatomic intervention on top of antibiotics, and the clean teaching point is the abscess-size threshold: pericolic abscesses under four centimeters typically resolve with antibiotics alone because antibiotic penetration is adequate and the host clears the residual, while abscesses four centimeters or larger get drained percutaneously under imaging guidance because penetration into a larger cavity is inadequate. So the vignette is the stable patient with a five-centimeter pericolic abscess, where the answer is intravenous antibiotics plus percutaneous drainage, not antibiotics alone and not urgent sigmoidectomy. Free perforation with diffuse peritonitis, purulent or feculent, is an urgent surgical indication, as is an undrainable abscess or deterioration on antibiotics, and the operation is sigmoidectomy, either with primary anastomosis in the stable patient with purulent contamination, or as a two-stage Hartmann procedure, meaning resection with an end colostomy and a closed rectal stump, for the unstable patient or a heavily contaminated field, with primary anastomosis preferred when stability allows because the colostomy reversal is a second operation with imperfect reversal rates. Fistulas are a separate elective category: the colovesical fistula is the most common and presents with air and stool in the urine and recurrent polymicrobial urinary infections, the colovaginal is second especially after hysterectomy, and all of them won't heal medically and are repaired with sigmoidectomy and closure of the tract, while strictures from chronic inflammation may obstruct and need resection.
Recurrence is the second big paradigm shift. After a first episode the recurrence rate is meaningful and rises with each subsequent episode, but the critical observation is that most recurrences are themselves uncomplicated. The old surgical rule was elective resection after two or three episodes, on the theory that complication risk rose with episode count, but the data didn't support it, because most recurrences stay uncomplicated, the risk of an emergent complicated episode doesn't rise dramatically with count in immunocompetent patients, and elective resection carries its own morbidity. So the current position is that prophylactic surgery after a fixed number of episodes is no longer recommended in immunocompetent patients, and elective resection is reserved for three specific groups: patients with multiple debilitating recurrences where the symptom burden itself is the indication, offered as a quality-of-life decision rather than because the next episode is predicted to be complicated; patients with prior complicated attacks like abscess, fistula, or stricture, who've demonstrated a more aggressive phenotype; and immunocompromised patients, in whom recurrence carries higher complicated-disease risk.
The post-episode counseling targets modifiable risk factors, with smoking, obesity, NSAIDs, corticosteroids, and opiates the strongest, smoking and obesity independent risk factors, NSAIDs and steroids increasing perforation risk in particular, and opiates possibly slowing motility enough to compound the obstruction at the diverticular neck, while aspirin doesn't drive the disease, so the patient on aspirin for cardiovascular reasons shouldn't stop it. Mesalamine, rifaximin, and probiotics have been studied for prevention with conflicting evidence and none is recommended, so the patient asking about a preventive pill gets the answer that no medication has shown reproducible benefit and the modifiable-risk-factor list is where the evidence lives. And colonoscopy six to eight weeks after a first episode is mandatory unless there's been a recent high-quality one, because CT can't reliably distinguish acute diverticulitis from a perforating sigmoid cancer in the inflamed segment, so the missed cancer is a recurring board failure mode, and the six-to-eight-week interval lets the inflammation resolve so the mucosa can be evaluated cleanly.
Segmental colitis associated with diverticulosis lives in this chapter because it's a chronic inflammatory pattern that mimics inflammatory bowel disease, and the candidate who doesn't recognize the segmental distribution will misdiagnose it. The inflammation is confined to the mucosa between the diverticula in the sigmoid, with the rectum spared, distinguishing it from ulcerative colitis, and the proximal colon spared, distinguishing it from Crohn's. The presentation is bleeding, mild diarrhea, mucus, and left-lower-quadrant cramping in a patient with known diverticulosis, and colonoscopy shows inflammation limited to the diverticular segment with normal mucosa immediately above and below. The histology mimics IBD, so the trap is the pathologist who reads the biopsy in isolation and signs out chronic colitis suggestive of IBD, and the diagnosis rests on the segmental distribution, not the histology alone. Treatment mirrors mild distal ulcerative colitis, with mesalamine producing response in most patients, budesonide or systemic steroids for refractory disease, and resection reserved for medically refractory cases. So the vignette is a patient in their sixties with known sigmoid diverticulosis, months of intermittent bleeding and mild diarrhea, and colonoscopy showing segmental sigmoid inflammation with a normal rectum and proximal colon, where the diagnosis is this segmental colitis, not ulcerative colitis, and the treatment is mesalamine.
A few vignettes pull it together. The young Asian patient with right-lower-quadrant pain and CT showing a right-colon diverticulum with surrounding inflammation and a normal appendix is right-sided diverticulitis, not appendicitis, and the management is otherwise identical to left-sided uncomplicated disease. The patient with recurrent uncomplicated diverticulitis is one in whom modifiable risk factors and quality of life drive the elective surgery conversation. And the immunocompromised patient with a first uncomplicated episode is not a candidate for selective antibiotics, and after recovery is a candidate for elective resection consideration because their next recurrence carries higher complicated-disease risk.
So the way to think about it is that diverticular management is graded by complication, by host immunocompetence, and by the symptom burden the patient is actually carrying. The diverticulosis itself is a wear pattern most patients never feel. Acute uncomplicated diverticulitis in an immunocompetent outpatient is now an inflammatory process treated with supportive care and selective antibiotics, not reflex antibiotics. Complicated disease grades on Hinchey, with management splitting at the four-centimeter abscess threshold and at the perforation line. Recurrence is common but mostly uncomplicated, and elective surgery is reserved for debilitating recurrence, prior complicated disease, or immunocompromise rather than episode count. And the segmental colitis is the IBD mimic that lives in the diverticular segment and responds to mesalamine.
The next chapter turns to pelvic floor and anorectal disorders, where the disease shifts from inflammation and infection to the mechanics of evacuation and continence: chronic constipation and its prescription therapies, the defecation disorders that respond to biofeedback, slow-transit constipation that may need surgery, opioid-induced constipation and its targeted drugs, fecal incontinence, and benign anorectal disease, with the organizing question being how the constipation phenotype dictates the therapy and why the mechanical and pharmacologic options aren't interchangeable.