Urgent considerations
See Differentials for more details
Certain complications of acute diarrhoea require urgent evaluation and treatment.
Volume depletion and electrolyte disturbances
These are the most common complications of acute diarrhoea. Children and older adults are at high risk. With children, the carer may not be replacing the fluid loss in a timely manner. Volume depletion manifests with increased thirst, decreased urinary output with dark urine, inability to sweat, and orthostatic symptoms. In severe cases, it may lead to acute renal failure and mental status changes (confusion and drowsiness). Cholera gravis in Vibrio cholerae infection may cause severe volume depletion, electrolyte disturbance, and arrhythmias. Prompt correction of hydration is required using low-osmolarity oral rehydration solution and isotonic intravenous fluid if oral or nasogastric intake is impaired.[5] In children, zinc supplementation is recommended as an adjunct to oral rehydration.[49] The use of the antisecretory agent racecadotril adjunctively with oral rehydration solution has been shown to diminish stool output safely, when studied in children up to the age of 10 years.[7]
Colonic perforation
This occurs principally in infants or severely malnourished patients and can be seen with Clostridioides difficile, Salmonella, and Shigella infections.[50] Urgent surgery is the treatment of choice.
Toxic megacolon
The pathogenesis of this complication is unclear; it occurs in the setting of pancolitis. Broad-spectrum antibiotic use may lead to C difficile infection with the associated complications of toxic megacolon, sepsis, perforation, and death. Toxic megacolon can also be seen with Shigella, cytomegalovirus (CMV), or Yersinia infection, and in ulcerative colitis and Crohn's disease.[51] In patients with known ulcerative colitis, toxic megacolon can be precipitated by superimposed infection. Treatment consists of supportive therapy with intravenous fluids, bowel rest, and total parenteral nutrition. Specific targeted therapy based on the underlying aetiology is given, such as corticosteroids in ulcerative colitis, antiviral agents in CMV colitis, and C difficile active antibiotics, or colectomy, in C difficile infection.
Intestinal obstruction and complications
This can occur in Shigella infections, helminth infections, and opportunistic infections in patients with AIDS. Crohn’s disease can also present with acute intestinal obstruction, intestinal perforation, peritonitis, and intra-abdominal abscess formation. The presenting symptoms are of crampy abdominal pain, nausea, vomiting, and abdominal distension. Treatment consists of nasogastric suction, strict nothing by mouth, and intravenous fluids. Antiparasitics and antibiotics may be needed, and surgery is considered if medical management fails.
Complications in other organs, bacteraemia, and sepsis
This can occur in severe infection. The normal microbiota may translocate across an inflamed colonic epithelium into the bloodstream. Endocarditis and osteomyelitis may complicate Salmonella infection. Myocarditis, glomerulonephritis, liver failure, peritonitis, and suppurative appendicitis may complicate Yersinia infection. Yersinia infection may also be mistaken for acute appendicitis. C difficile infection may lead to profound bowel necrosis, multiple organ failure, and death. Antibiotic treatment and supportive care is indicated in cases of severe infectious diarrhoea especially when additional complications arise. Specifically, colon resection is sometimes necessary in severe C difficile-induced bowel necrosis.
Sepsis is a spectrum of disease, where there is a systemic and dysregulated host response to an infection.[52] Presentation ranges from subtle, non-specific symptoms (e.g., feeling unwell with a normal temperature) to severe symptoms with evidence of multi-organ dysfunction and septic shock. It is important to consider the possibility of sepsis in any patient with symptoms or signs that indicate possible infection (e.g., acute diarrhoea).[53] Patients may have signs of tachycardia, tachypnoea, hypotension, fever or hypothermia, poor capillary refill, mottled or ashen skin, cyanosis, newly altered mental state or reduced urine output.[53] Sepsis and septic shock are medical emergencies.
Risk factors for sepsis include: age under one year, age over 75 years, frailty, impaired immunity (due to illness or drugs), recent surgery or other invasive procedures, any breach of skin integrity (e.g., cuts, burns), intravenous drug misuse, indwelling lines or catheters, and pregnancy or recent pregnancy.[53]
Early recognition of sepsis is essential because early treatment improves outcomes.[53][54][Evidence C][Evidence C] However, detection can be challenging because the clinical presentation of sepsis can be subtle and non-specific. A low threshold for suspecting sepsis is therefore important. The key to early recognition is the systematic identification of any patient who has signs or symptoms suggestive of infection and is at risk of deterioration due to organ dysfunction. Several risk stratification approaches have been proposed. All rely on a structured clinical assessment and recording of the patient’s vital signs.[53][56][57][58][59] It is important to check local guidance for information on which approach your institution recommends. The timeline of ensuing investigations and treatment should be guided by this early assessment.[58]
Treatment guidelines have been produced by the Surviving Sepsis Campaign and remain the most widely accepted standards.[54][60] Recommended treatment of patients with suspected sepsis is:
Measure lactate level, and remeasure lactate if initial lactate is raised (>2 mmol/L)
Obtain blood cultures before administering antibiotics
Administer broad-spectrum antibiotics (with methicillin-resistant Staphylococcus aureus [MRSA] coverage if there is high-risk of MRSA) for adults with possible septic shock or a high likelihood for sepsis
For adults with sepsis or septic shock at high-risk of fungal infection, empiric antifungal therapy should be administered
Begin rapid administration of crystalloid fluids for hypotension or lactate level ≥4 mmol/L. Consult local protocols
Administer vasopressors peripherally if hypotensive during or after fluid resuscitation to maintain mean arterial pressure (MAP) ≥65 mmHg, rather than delaying initiation until central venous access is secured. Noradrenaline (norepinephrine) is the vasopressor of choice
For adults with sepsis-induced hypoxemic respiratory failure, high flow nasal oxygen should be given
Ideally these interventions should all begin in the first hour after sepsis recognition.[60]
For adults with possible sepsis without shock, if concern for infection persists, antibiotics should be given within 3 hours from the time when sepsis was first recognised.[54] For adults with a low likelihood of infection and without shock, antibiotics can be deferred while continuing to closely monitor the patient.[54]
For more information on sepsis, please see Sepsis in adults and Sepsis in children.
Neurological problems
Seizure is the most common neurological complication. It is a well-recognised complication of Shigella infection. Encephalopathy with lethargy, confusion, and headache can be seen. Obtundation or coma and abnormal neurological signs, including posturing, are rare. In cases of fatal encephalopathy, cerebral oedema has been found at autopsy. Delirium and coma may be present in Salmonella infection. Guillain-Barre syndrome may be seen as a late complication in Campylobacter enteritis. Listeria infection can cause meningitis.
Reactive arthritis
This may be seen alone or in association with conjunctivitis and urethritis, a triad formerly known as Reiter's syndrome.[61] It may be seen in Shigella, Salmonella, Campylobacter, and Yersinia infections. The arthritis is a sterile inflammatory arthritis. Treatment is usually supportive with non-steroidal anti-inflammatory drugs.
Haemolytic uraemic syndrome (HUS) and thrombotic thrombocytopenic purpura (TTP)
HUS presents with haemolysis and acute renal failure, while TTP presents with fever, haemolytic anaemia, thrombocytopenia, renal failure, and neurological changes. They can occur in infections with enterohaemorrhagic E coli and, less commonly, Shigella, particularly in young children and older adults who are exposed to antibiotics and antidiarrhoeal agents. Rare cases of HUS withCampylobacter and Aeromonas have also been reported. Treatment is supportive, but plasma exchange and glucocorticoids could be considered. Antibiotics should be avoided in infections secondary to enterohaemorrhagic E coli, as it is unclear if they increase risk of HUS.[20]
Hepatic necrosis
This is rarely associated with Bacillus cereus infection.[62]
Enteritis necroticans
Clostridium perfringens can cause enteritis necroticans (pigbel).[63]
Listeria infection in pregnancy
Listeriosis should be suspected in pregnant women with presumptive Listeria exposure based on ingestion of high-risk foods such as unpasteurised dairy products, unwashed fruits, improperly heated hot dogs or deli meats, and symptoms (including myalgia, abdominal or back pain, nausea, vomiting, or diarrhoea with or without fever ≥38.1°C [100.6°F]). The incidence of listeriosis associated with pregnancy is approximately 10 to 20 times higher than in the general population and it is diagnosed most commonly during the third trimester.[64][65] Outcomes of Listeria infection in pregnant women are typically good, but it can lead to fetal death, premature birth, or infected newborns. Early treatment has been shown to improve fetal and neonatal outcomes; consult local protocols for guidance.[65]
Gangrenous bowel
Ischaemic colitis may result in gangrenous bowel. The patient may develop severe volume depletion and shock, and require surgical intervention.
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