Diverticulitis vs. diverticulosis

Diverticulitis vs. Diverticulosis: What's the difference, and when is it dangerous?

Many people confuse diverticulosis and diverticulitis - but the difference is crucial. The first is a common, usually harmless condition. The second is an acute inflammation that may require hospital admission or surgery.

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Diverticulosis: Small pouches in the large intestine

Diverticula are small pouches (typically 5-10 mm) in the bowel wall, which form at weak points where blood vessels penetrate the muscle layer. They are predominantly found in the sigmoid colon (the S-shaped part of the large intestine).

The prevalence rises clearly with age. Diverticula are unusual before the age of 40 and become common in older people; United States surveys describe more than half of people over 60 as having diverticula [1]. These figures come from American data, not Danish registers. Most are discovered incidentally during a colonoscopy or CT scan.

Risk factors include:

• Low fibre intake and a Western diet [2]
• Obesity and physical inactivity [3]
• Smoking and NSAID use [4]
• Genetic predisposition. In a Swedish twin study, heritable factors explained around 40% of the variation in risk at population level, not in the individual [5]

Read also our article on diverticulosis.

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Diverticulitis: When a pouch becomes inflamed

Older estimates of a 10-25% lifetime risk after diverticulosis is found are now considered too high. In a retrospective US VA study of patients with incidentally found diverticulosis, 4.3% developed diverticulitis over an average of 11 years of follow-up using a broad definition, while 1% met a strict definition requiring imaging or operative confirmation [6]. The results cannot simply be transferred to all patient groups. Diverticulitis is an acute inflammation or micro-perforation of a diverticulum, and the condition is divided into:

• Uncomplicated diverticulitis (the large majority of cases): Localised inflammation without an abscess, perforation, or fistula
• Complicated diverticulitis (around 20% of cases in published series): Abscess, free perforation, obstruction, or fistula

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Symptoms

• Persistent pain in the lower left part of the abdomen ("left-sided appendicitis")
• Fever and elevated CRP
• Change in bowel habits (constipation or diarrhoea)
• Nausea, bloating
• With complications: severe pain, signs of peritonitis, urinary symptoms (fistula to the bladder)

The diagnosis is confirmed with a CT scan of the abdomen, which also classifies the severity using the Hinchey classification (originally described by Hinchey et al. [7], now applied in a CT-based form according to international surgical guidelines [11]).

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Treatment of uncomplicated diverticulitis

Previously, almost all cases were treated with antibiotics and hospital admission. Modern Danish and European guidelines now recommend:

• Outpatient treatment without antibiotics in selected patients (immunocompetent, without complications, CRP <140, no fever) [8]
• Rest, clear fluids gradually progressing to a normal diet
• Pain relief (paracetamol; avoid NSAIDs)

The landmark AVOD study (Sweden) and the Dutch DIABOLO study have documented that antibiotics do not speed up recovery or reduce complications in uncomplicated diverticulitis [9,10].

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Treatment of complicated diverticulitis

• Abscess <4 cm: Antibiotics alone are often sufficient
• Abscess ≥4 cm: Percutaneous drainage + antibiotics
• Perforated diverticulitis with diffuse peritonitis: In perforated diverticulitis with diffuse peritonitis the surgical method depends on haemodynamic stability, comorbidity and the operative findings. WSES recommends a Hartmann's procedure in critically ill patients and in selected patients with significant comorbidity. In clinically stable patients without significant comorbidity, primary resection with anastomosis, with or without a diverting stoma, may be considered. The specific method is decided during the acute surgical care [11]
• Free air without diffuse peritonitis: Free air on CT without diffuse intra-abdominal fluid or peritonitis does not automatically mean the same treatment. In carefully selected, clinically stable patients, non-operative management with close monitoring may be possible [11]
• Recurrent or complicated cases: A planned elective sigmoid resection is considered - but NOT routinely after 2 attacks as was previously the case; the decision is made on an individual basis [11, 12]

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Prevention

• Fibre in the diet: In the EPIC-Oxford cohort of 47,033 UK adults followed for a mean of 11.6 years, participants in the highest fifth of fibre intake had fewer hospital admissions or deaths from diverticular disease than those in the lowest fifth [13]. This is an observed association in a cohort of health-conscious participants, not proof that fibre prevents the disease, and no gram target is given here. How much fibre suits you depends on your symptoms and your other treatment
• Physical activity and a normal weight
• Avoid smoking and frequent NSAID use
• It was previously recommended to avoid nuts, seeds, and popcorn - this has now been disproven and is no longer advised against [14]

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When should you contact a doctor?

Seek medical advice for:

• Persistent pain in the lower left abdomen for more than 24 hours
• Fever accompanied by abdominal pain
• Severe bleeding from the rectum
• Signs of peritonitis (rigid abdomen, severe pain, feeling generally unwell) → call 112

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References

1. Peery AF, et al. Burden and cost of gastrointestinal, liver, and pancreatic diseases in the United States. Gastroenterology 2019;156(1):254-72.
2. Aune D, et al. Dietary fibre intake and the risk of diverticular disease: a systematic review and meta-analysis. Eur J Nutr 2020;59(2):421-32.
3. Strate LL, et al. Obesity increases the risks of diverticulitis and diverticular bleeding. Gastroenterology 2009;136(1):115-22.
4. Humes DJ, et al. Smoking and the risk of diverticular disease. Aliment Pharmacol Ther 2011;34(8):988-94.
5. Granlund J, et al. The genetic influence on diverticular disease - a twin study. Aliment Pharmacol Ther 2012;35(9):1103-7.
6. Shahedi K, et al. Long-term risk of acute diverticulitis among patients with incidental diverticulosis. Clin Gastroenterol Hepatol 2013;11(12):1609-13.
7. Hinchey EJ, et al. Treatment of perforated diverticular disease of the colon. Adv Surg 1978;12:85-109.
8. Schultz JK, et al. European Society of Coloproctology: guidelines for the management of diverticular disease of the colon. Colorectal Dis 2020;22(Suppl 2):5-28.
9. Chabok A, et al. Randomized clinical trial of antibiotics in acute uncomplicated diverticulitis (AVOD). Br J Surg 2012;99(4):532-9.
10. Daniels L, et al. Randomized clinical trial of observational versus antibiotic treatment for a first episode of CT-proven uncomplicated acute diverticulitis (DIABOLO). Br J Surg 2017;104(1):52-61.
11. Sartelli M, et al. 2020 update of the WSES guidelines for the management of acute colonic diverticulitis in the emergency setting. World J Emerg Surg 2020;15:32.
12. Hall J, et al. The American Society of Colon and Rectal Surgeons Clinical Practice Guidelines for the Treatment of Left-Sided Colonic Diverticulitis. Dis Colon Rectum 2020;63(6):728-47.
13. Crowe FL, et al. Diet and risk of diverticular disease in Oxford cohort of EPIC. BMJ 2011;343:d4131.
14. Strate LL, et al. Nut, corn, and popcorn consumption and the incidence of diverticular disease. JAMA 2008;300(8):907-14.

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Read also

Diverticula of the intestine - a comprehensive overview