Peritoneal Dialysis

Peritoneal dialysis (PD) uses the peritoneum as a semipermeable membrane: solutes are removed by diffusion down a concentration gradient into the dialysate, and water by osmosis (ultrafiltration) driven by an osmotic agent.

The effective exchange surface is the peritoneal capillary endothelium, described by the three-pore model — large pores, small pores and aquaporin-1 water channels (responsible for sodium sieving).

Access is by a Tenckhoff catheter placed surgically, laparoscopically or percutaneously, ideally 2 weeks before starting to allow the exit site to heal.

Glucose-based solutions (1.5%, 2.5%, 4.25%) are standard; icodextrin (a glucose polymer) gives sustained ultrafiltration over a long dwell and is ideal for the overnight or day-long dwell; amino-acid solutions address protein loss.

Low-glucose-degradation-product, neutral-pH, bicarbonate-buffered solutions are more biocompatible and better preserve the membrane and residual renal function.

CAPD (continuous ambulatory PD) — typically four exchanges of 2 litres daily, performed manually by the patient or carer.

APD (automated PD) by a cycler at night — including CCPD (continuous cycling PD), NIPD (nightly intermittent PD) and TPD (tidal PD). Nightly PD can be an alternative for more vulnerable elderly patients, including nursing home residents.

Peritoneal equilibration test (PET) classifies membrane transport as high, high-average, low-average or low, guiding dwell time: high transporters need short dwells (APD), low transporters need long dwells (CAPD).

Adequacy is assessed by symptoms, volume status and nutrition, with a weekly Kt/V urea of at least 1.7 as the conventional minimum; preservation of residual renal function is a priority.

PD is a satisfactory alternative for geriatric ESRD patients, and most studies confirm that elderly patients on PD and HD have similar survival.

PD is better than HD for patients with residual diuresis, severe hypotension, complicated or short-lived vascular access, intradialytic arrhythmias, angina, or cardiovascular instability.

Additional advantages: home-based therapy with independence and no travel, gentle continuous solute and fluid removal without haemodynamic swings, better preservation of residual renal function, no vascular access or systemic anticoagulation, a more liberal diet and fluid allowance, and better preservation of anaemia control.

In India, PD avoids repeated travel to a dialysis centre, is feasible in rural areas, and is supported by dedicated government guidelines — important where transport and caregiver time are major barriers.

The most frequent practical problems in older patients on PD are dialysate leakage, hernia formation, backache, difficulty in learning the technique, social isolation, family burn-out, and worsening of peripheral vascular disease or malnutrition.

Peritonitis is the major infective complication — cloudy effluent with abdominal pain, effluent white cell count >100/ µL with >50% neutrophils; treat with intraperitoneal antibiotics covering Gram-positive and Gram-negative organisms; recurrent, refractory or fungal peritonitis requires catheter removal.

Exit-site and tunnel infection, catheter malfunction and migration, constipation-related drainage failure.

Metabolic: glucose absorption causing hyperglycaemia, weight gain and dyslipidaemia; protein loss of 5–15 g per day in the effluent.

Encapsulating peritoneal sclerosis — a rare but devastating complication of long-duration PD.

Nutrition: malnutrition is frequently present; provide more than 1.2 g/kg body weight of protein daily for patients on PD (versus more than 1 g/kg for HD). Older patients on dialysis develop more serious bone disease than the young because of osteopenia, unbalanced diet, reduced physical activity and lack of sun exposure.

Relative contraindications: extensive abdominal adhesions or previous major abdominal surgery, active inflammatory bowel disease or diverticulitis, large irreparable hernia, stomas, severe respiratory disease, and — critically in geriatrics — inability of the patient or carer to perform exchanges safely, which is the commonest practical barrier.