A. Definitions

1. Diverticulum is an outpouching of a hollow tube, usually refers to colonic diverticula
   1. True diverticula include outpouching of the muscular wall
   2. Colonic diverticula are herniations of mucosa only through muscle - not true diverticula
2. The condition of having such a pouch in the colon is called Diverticulosis
   1. Diverticuli usually (>80%) found in left (descending) and sigmoid colon
   2. Right sided diverticuli are very uncommon in USA but more comon in Japan [1,3]
3. About 75% of diverticuli are asymptomatic
   1. A minority of remaining patients have various abdominal complaints
   2. Severe diverticular disease in 10-15% including diverticulitis, abscess, hemorrhage
4. Diverticulitis is inflammation of the diverticulum
   1. Microperforations present
   2. Can expand to frank abscess
   3. May evolve to fistula tract
5. Diverticular hemorrhage - bleeding rupture of diverticular arterial supply

B. Diverticulosis

1. Patient Population
   1. Middle age and elderly mainly
   2. Present in 20-30% of persons age >50
   3. Present in ~50% of persons age >70
   4. Present in >65% of persons age >80
2. Risk Factors
   1. Age
   2. Low fiber diets are strongly associated with the development of diverticuli
   3. Low physical activity is associated with divertiuli
3. Pathophysiology [2,3]
   1. Excessive smooth muscle activity predominates in early stage disease
   2. Cholinergic denervation hypersensitivity affects smooth muscle
   3. Upregulation of smooth muscle M3 receptors observed in all stages of disease
   4. Hyperreactivity to acetylcholine through increased M3 receptors may lead to diverticuli
4. 75-80% of patients never have symptoms (diverticuli detected for other reasons)
5. Symptomatic Diverticulosis
   1. Often associated with constipation
   2. Pain
   3. Tenesmus
   4. Colonic Bleeding
6. Diverticular Hemorrhage [1]
   1. Microangiopathy - intimal thickening and medial thinning in vasa recta
   2. Segmental weakening of the artery occurs, predisposing to rupture
   3. Causes of these changes in the diverticular arteries are not understood
   4. Typically presents as abrupt, painless onset; mild abdominal cramps possible
   5. Passage of voluminous red or maroon blood or clots (melana uncommon)
   6. Bleeding is usually self limited

C. Characteristics of Diverticulitis

1. All diverticulitis consists of at least microperforations
   1. Increased intestinal intraluminal pressure
   2. Weakening of bowel wall
2. Disease Progression (Stages)
   1. Stage I: small confined pericoloic abscesses, mild symptoms
   2. Stage II: larger pericolic abscesses, classic symptoms (localized)
   3. Stage III: generalized peritonitis is present
   4. Stage IV: fecal contamination of peritoneal cavity
3. Perforated Diverticulitis
   1. Perivesicular abscess has ruptured into peritoneal cavity
   2. This leads to purulent peritonitis
   3. No fecal contamination has occurred
   4. Therefore, this is stage III
4. Free Rupture
   1. Less common than perforation
   2. Uninflamed and unobstructed diverticulum ruptures into peritoneum
   3. This leads to gross fecal contamination
   4. Therefore, this is stage IV
5. Epidemiology
   1. Equal male and female; more prevalent in industrialized than developing nations
   2. Occurs in ~10% of adults >40 years and >50% in those >80 years
   3. About 130,000 hospitalizations per year in USA due to diverticulitis
   4. Affects sigmoid and descending colon in >90% of cases

D. Symptoms of Diverticulitis

1. Pain is present in nearly all cases
   1. Often begins in hypogastrium
   2. Then "moves" to abdominal left lower quadrant (LLQ) in Western countries
   3. Usually colicky or steady pain
   4. Pain may be referred to scrotum, penis or suprapubic region
   5. Free perforation leads to peritoneal irritation and marked, usually diffuse, abdominal pain
   6. For right sided (very uncommon in USA) lesions, RLQ pain may occur
2. Altered Bowel Movements
   1. Constipation more common than diarrhea
   2. Colonic obstruction may occur, only after recurrent acute cases
   3. Small intestinal functional obstruction (ileus) may occur depending on location
3. Fever - usually low grade, usually accompanied by leukocytosis
4. Bacteremia and Sepsis
   1. Tachycardia
   2. Hypotension
   3. Sepsis syndrome

E. Diagnosis

1. Clinical scenario: at risk population, symptoms, signs, laboratory
2. Computerized Tomographic Scan (CT) scan
   1. Radiologic test of choice with sensitivity ~95% and specificity ~100%
   2. Delineation of extent of disease process
   3. Differentiating from carcinoma may be enhanced with oral contrast agent
   4. Presence of diverticula, inflammation of pericolic fat or other tissues, bowel wall thickness >4mm, peridiverticular abscess strongly suggests diverticulitis
3. Colonosocopy or sigmoidoscopy
   1. Avoided in acute situation as they may exacerbate disease process; cause perforation
   2. Recommended ~6 weeks after acute process dies down to evaluate for other disorders
4. Abdominal Radiograph
   1. Evaluation for air in abdominal cavity
   2. Presence of air usually means perforation
   3. All patients have air following abdominal surgery
5. Laboratory
   1. Elevation in ESR, C-reactive protein, thrombocytosis
   2. Elevation in white cell count (WBC) with predominant neutrophilia
   3. Immature neutrophil (band) forms may be present
   4. Albumin may be reduced
   5. Must assess for electrolyte imbalances
   6. Dehydration (increased BUN to creatinine ratio) is common
   7. Urinalysis: pneumaturia, bactiuria may be present with colovesicular fistula formation
6. Hinchey Staging [2]
   1. Stage 1: small, confined pericolic or mesenteric abscesses
   2. Stage 2: larger abscesses often confined to pelvis
   3. Stage 3 (perforation): peridiverticular abscess has ruptured causing purelent peritonitis
   4. Stage 4 (free rupture): rupture of uninflamed and unobstructed diverticulum into free peritoneal cavity with fecal contamination
7. Differential Diagnosis
   1. Acute appendicitis
   2. Inflammatory bowel disease (IBD) - especially Corhn's disease
   3. Pelvic inflammatory disease (PID)
   4. Tubal pregnancy
   5. Cystitis
   6. Advanced colonic cancer
   7. Infectious colitis
8. Diverticular Hemorrhage
   1. Diagnosed with red cell scan and/or angiography
   2. Red cell scan scintigraphy has sensitivty to 0.1mL/min bleeding
   3. Angiography has sensitivity to 0.5mL/min bleeding

F. Complications

1. Macroperforation leading to peritonitis
2. Large abscess formation
3. Intestinal stricture
4. Fistula
   1. Intraintestinal
   2. Colovesicular
   3. Vesicular fistulae may be associated with recurrent UTI, pneumouria
5. Obstruction

G. Treatment of Diverticulitis

1. Mild cases may be treated as outpatients
   1. To avoid hospitalization, patient must tolerate oral intake with liquid diet
   2. Low fever usually with <15,000K/µL leukocytes
   3. Broad spectrum oral antibiotics for ~10 days
   4. Ciprofloxacin + metronidazole commonly used
   5. Oral analgesia can be given with great care (caution to induce ileus)
   6. Analgesics may mask worsening pain, increase constipation / perforation
   7. Avoid non-steroidal anti-inflammatory drugs (NSAIDs) with relative dehydration
   8. Symptomatic improvement should occur in 2-3 days or re-evaluation recommended
   9. Patients requiring narcotic analgesics should generally be hospitalized
2. Moderate Disease
   1. Need for intravenous (IV) fluids, parenteral narcotics
   2. Nothing by mouth (NPO)
   3. Nasogastric Tube placed (decompression)
   4. Analgesia: opiates are usually given parenterally
   5. Avoid morphine sulfate, which causes colonic spasm
   6. Meperidine (Demerol®) is usually used (may reduce seizure threshhold)
   7. Hydration: follow acid-base status
   8. If no improvement within 2-3 days, repeat CT is appropriate
   9. Percutaneous drainage may be useful for patients with >4cm abscess (stage 2)
3. Antibiotics
   1. Inpatient: Ampicillin + Gentamicin (or Ceftriaxone) + Metronidazole
   2. Alternative: imipenem + cilistatin or meropenam or piperacillin + tazobactam (Zosyn®)
   3. Cefoxitin alone is no longer recommended
   4. Broad spectrum IV antibiotics are recommended for 5-7 days (as effective as longer treatment)
   5. Then switch to oral
4. Percutaneous needle drainage
   1. Consider in patients with peridiverticular abscesses of >4cm
   2. Often permits surgery to be performed electively; reduces symptoms and signs
   3. Increases likelihood that one-stage surgery (partial colectomy) will be successful
   4. Abscess cavities containing gross feculent material should undergo early surgery
5. Surgical Considerations
   1. Up to 20% of patients with moderate or severe diverticulitis will require surgery
   2. Pain, symptom relief, and leukocytosis begin to resolve in <72 hours
   3. If these findings do not begin to resolve in <72 hours, surgery may be needed
   4. Single stage procedures are now often possible [1]
   5. Laparoscopic colectomy has reported successful in stage 1 or 2 disease
   6. Fewer than 10% of patients with acute diverticulitis will require same-admission surgery
   7. Complications of diverticulitis (see above) are generally treated surgery
6. Indications for Emergency Surgery
   1. Generalized peritonitis
   2. Uncontrolled sepsis
   3. Uncontained vsceral performation
   4. Presence of large, undrainable (inaccessible) abscess
   5. ck of improvement, or deterioration, within 3 days of antibiotic and standard therapy

H. Follow Up

1. Recurrence rate ~20% and these often do not respond to conservative medical therapy
2. Recommend low fat, high fiber (vegetable and fruit better than cereal fiber) diet
3. Stool softeners (such as docusate, Colace®) may be useful
4. Colonoscopy should be performed after all inflammation resolved if hasn't been done recently
5. Patients with frequent recurrences may benefit from surgery

References

1. Stollman N and Raskin B. 2004. Lancet. 363(9409):631
2. Jacobs DO. 2007. NEJM. 357(20):2057
3. Golder M, Burleigh DE, Belai A, et al. 2003. Lancet. 361(9373):1945