Factors affecting body weight development and eating behaviour in patients on continuous ambulatory peritoneal dialysis treatment

Continuous ambulatory peritoneal dialysis (CAPD) and hemodialysis (HD) have different metabolic effects in dialysis patients, since absorption of intraperitoneal glucose implies an additional energy source in CAPD patients. In spite of this, protein-energy malnutrition is known to occur frequently, both in patients on hemodialysis and in patients on CAPD, and an association with increased morbidity and mortality is well established. It is therefore of great importance to identify factors which have the potential of negatively influencing the nutritional state.

In this thesis, it is demonstrated that taste acuity of primary tastes in end-stage renal disease (ESRD) patients is hampered in the form of increased recognition thresholds. The taste thresholds were significantly higher for salt and bitter in preuremic patients, compared to control subjects. In CAPD patients, taste recognition of bitter was impaired and in HD patients, recognition of salty taste was impaired. Patients with ESRD have significantly fewer fungiform taste buds, which might be an important factor contributing to the impaired taste acuity. In addition to the study of the number of taste buds, the presence of peripheral nervous tissue in taste buds with the aid of specific markers (primary antibodies) was also analysed. With these antibodies, no major immunohistochemical differences were disclosed between uremic patients and healthy controls. In a study of energy intake in CAPD patients (five days food recording), it is also established that dietary energy intake from carbohydrates, protein and fat is lower in patients treated with CAPD than in those treated with hemodialysis, although the energy percentage composition of the dietary macronutrients is unaffected.

Transperitoneal energy intake compensates for this lower dietary energy intake, and makes total energy intake almost the same in CAPD and HD patients, but with a change in the composition of the diet of CAPD patients towards a significantly higher carbohydrate percentage in energy intake. The level of total energy intake observed places both patient groups in the risk zone for developing malnutrition. CAPD patients have a slower gastric emptying rate, as measured with scintigraphy. This impairment of gastric emptying rate correlates with disturbances in the normal myoelectric rhythm of the stomach (tachygastria), as measured with electrogastrography.

A body composition analysis of CAPD patients, as studied with computed tomography of the abdomen and of the right thigh, as well as with dual energy x-ray absorptiometry, reveals an increase in the intraabdominal fat area after commencement of peritoneal dialysis. Thus CAPD induces a distribution of body fat that resembles the pattern observed in the metabolic syndrome.

In conclusion, several factors which have the potential of negatively influencing the nutritional state in CAPD patients have been identified. Moreover, a metabolic consequence in the form of an increase in intraabdominal fat is demonstrated in patients treated with CAPD, which may accelerate the development of risk factors for cardiovascular disease.