What causes diarrhea in patients undergoing dialysis?

Causes of Diarrhea in Dialysis Patients

Diarrhea in dialysis patients is most commonly caused by medications (particularly antibiotics leading to Clostridium difficile infection), followed by medication-related adverse effects, constipation with overflow diarrhea from opioids and phosphate binders, and less commonly by ischemic colitis, inflammatory bowel disease, or laxative overuse.

Medication-Related Causes

Clostridium difficile Infection (Most Common Infectious Cause)

• C. difficile is by far the most common enteric cause of fever and diarrhea in dialysis patients, particularly those who received antibiotics or chemotherapy within 60 days before diarrhea onset 1
• C. difficile accounts for 10-25% of all antibiotic-associated diarrhea cases and virtually all cases of antibiotic-associated pseudomembranous colitis 1
• Testing for C. difficile toxin should be performed in any dialysis patient with diarrhea who has recent antibiotic exposure 1
• Some patients may present with ileus, toxic megacolon, or leukocytosis without diarrhea, especially postoperative patients 1

Inappropriate Medication Dosing

• Medications requiring renal dose adjustment (such as acyclovir and gabapentin) are frequently prescribed at inappropriately high doses in dialysis patients, leading to adverse effects including gastrointestinal symptoms 1
• Medication reconciliation failures at transitions of care commonly result in dosing errors that can cause diarrhea 1

Laxative Overuse

• Chronic and excessive laxative use can cause melanosis coli and severe chronic diarrhea in peritoneal dialysis patients 2
• This is a diagnosis of exclusion but should be considered when other causes are ruled out 2
• In peritoneal dialysis patients specifically, chronic diarrhea from any cause increases the risk of bacterial translocation leading to peritonitis 2

Constipation-Related Overflow Diarrhea

Opioid-Induced Constipation

• Dialysis patients frequently receive opioids for pain management, which commonly cause severe constipation 1
• When bowel regimens are discontinued (particularly during care transitions), severe constipation can develop with paradoxical overflow diarrhea 1
• The combination of opioids with phosphate binders (which also cause constipation) compounds this risk 1

Phosphate Binder Effects

• Sodium phosphate enemas and high-dose phosphate binders can cause both constipation and subsequent diarrhea 1
• Inappropriate continuation of phosphate binders during episodes of hypophosphatemia can worsen gastrointestinal symptoms 1

Ischemic Colitis

• Dialysis patients have increased risk of ischemic colitis due to arteriosclerosis, hemodynamic instability during dialysis, and end-stage kidney disease itself 3
• Ischemic colitis can present with bloody diarrhea and may be difficult to distinguish from infectious or inflammatory causes 3
• In peritoneal dialysis patients specifically, ischemic colitis has been reported and may improve with switching to hemodialysis 4
• Barium enema may show rigidity, mucosal irregularity, and "thumb print" appearance 4

Inflammatory Bowel Disease

• Ulcerative colitis can present atypically in dialysis patients with rectal sparing or segmental distribution, making diagnosis challenging 3
• Inflammatory bowel disease may be masked by concurrent C. difficile infection or ischemic colitis 3
• The NKF-K/DOQI guidelines note that inflammatory or ischemic bowel disease represents a relative contraindication to peritoneal dialysis due to increased risk of transmural contamination by enteric organisms 1
• Frequent episodes of diverticulitis during peritoneal dialysis often result in peritonitis 1

Dialysis-Specific Mechanical Causes (Peritoneal Dialysis)

• Peritoneal leakage into the rectum increases contamination risk and can cause diarrhea 1
• Intolerance to peritoneal dialysis volumes may cause gastrointestinal symptoms 1

Critical Clinical Pitfalls

Volume Depletion Risk

• Diarrhea combined with excessive ultrafiltration from dialysis exchanges can rapidly cause hypovolemic shock, electrolyte imbalance, and metabolic acidosis 2
• Volume depletion is a frequently identified risk factor for diarrhea-related deaths in all age groups 1

Diagnostic Challenges

• Other infectious causes (Salmonella, Shigella, Campylobacter, STEC) are uncommon in dialysis patients unless present on admission or in outbreak settings 1
• Sending stool cultures for routine bacterial pathogens or ova and parasites should generally be avoided unless the patient was admitted with diarrhea or is HIV-infected 1
• Multiple overlapping etiologies can coexist, making diagnosis difficult 3

Peritoneal Dialysis-Specific Risks

• Chronic diarrhea of any duration in peritoneal dialysis patients increases the risk of bacterial translocation and peritonitis 2
• Inflammatory bowel disease and frequent diverticulitis are relative contraindications to continuing peritoneal dialysis 1

Diagnostic Approach

• Test specifically for C. difficile toxin in any patient with recent antibiotic exposure 1
• Review all medications for inappropriate dosing and potential gastrointestinal adverse effects 1
• Assess for constipation with overflow diarrhea, particularly in patients on opioids and phosphate binders 1
• Consider colonoscopy with biopsy when diarrhea is intractable or when ischemic colitis or inflammatory bowel disease is suspected 3
• Evaluate medication lists for excessive laxative use 2