1 Division of Nephrology, Department of Medicine and 2 Department of Radiology, Veterans General Hospital, Taipei and 3 National Yang-Ming University, School of Medicine, Taiwan
Correspondence and offprint requests to: Der-Cherng Tarng, MD, Division of Nephrology, Department of Medicine, Veterans General Hospital, No. 201, Sec 2, Shih-Pai Road, Taipei 11217, Taiwan.
Keywords: haemodialysis; malnutrition; megacolon; stool impaction
Introduction
Malnutrition is prevalent among patients receiving chronic haemodialysis (HD). The mechanism of malnutrition has not been fully understood, but several factors could be involved [1]. We present an interesting case with an important but easily overlooked cause of malnutrition.
Case report
A 63-year-old Chinese woman presented in 1995 with end-stage renal failure as a consequence of diabetic nephropathy. She started on regular HD thrice a week at an outpatient HD facility. Multi-infarct dementia developed in the recent years and prevented her from self-care. In April 1996, poor appetite and general malaise were initially noted. Predialysis laboratory investigations showed total protein of 6.1 g/dl, albumin 3.1 g/dl, transferrin 183 mg/dl, blood urea nitrogen 32 mg/dl, creatinine 3.9 mg/dl, white cell count 10700/mm3 with neutrophil 80.5% and lymphocyte 9.0% and a haemoglobin of 9.6 g/dl despite recombinant erythropoietin at a maintenence dose of 100 I.U./kg/week. The mean value of Kt/Vurea [2] was 0.85 due to a decrease in the flow of arteriovenous fistula (AVF) upon HD sessions. Initially, inadequate dialysis leading to malnutrition was considered. She underwent a fistulography, which revealed incomplete occlusion at the venous anastomosis of AVF. After percutaneous transluminal angioplasty for stenotic AVF lesion and intensified HD, however, the patient still did not feel well. She was referred to our institution in June 1996.
On examination, the patient appeared severely malnourished and demented. Abdomen was distended with slightly increased bowel sounds. Rectal examination revealed megarectum full of stools. Further history from her family disclosed problems with chronic constipation. A plain abdominal radiograph demonstrated markedly distended rectum and sigmoid colon with fecal impaction which displaced the contraceptive device outward, suggesting a diagnosis of megacolon (Figure 1). Anorectal manometry revealed a resting pressure at 70 mmHg; both the compression pressure and squeeze pressure were poor. First sensation was obtained at 200 ml, urgency at 250 ml and maximal capacity at 800 ml. The results confirmed that her capacious rectum required an increased distention volume before internal anal sphincter relaxation occurred. Presence of rectoanal inhibitory reflex excluded Hirschsprung's disease.
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Gastrointestinal (GI) symptoms such as nausea, constipation and diarrhoea occur frequently in patients with diabetes mellitus. In many cases these symptoms are thought to be related to abnormal GI motility due to diabetic autonomic neuropathy involving the GI tract [3]. In patients with chronic renal failure, disturbances in fluid and electrolytes, inactivity, and the use of calcium preparations, aluminum-containing phosphate binders and ion exchange resins predispose to stool impaction [4]. Furthermore, the effects of uraemia and diabetes on the autonomic nervous system contribute to the risk [5].
Megacolon can be broadly divided into two main groups according to whether or not ganglia are present in the intermuscular plane of the rectal wall. The complete absence of ganglia, even along a short segment of rectum, indicates Hirschspriung's disease. Otherwise, megacolon may be secondary to some predisposing factors, such as a stricture, a corda equina lesion and chronic constipation of any cause, there may even be no obvious organic reason [6]. Megacolon in patients on chronic HD had rarely been reported. It is speculated that our patient had daily accumulations of stool in the rectum and sigmoid colon to such a degree that resulted in megacolon to accommodate the huge fecal impaction. The management of megacolon is conservative in the first sense. Laxatives, enema, or suppositories, often in combination, are required to keep the colon empty. Most of the patients can be effectively managed by initial disimpaction, followed by long-term osmotic laxatives. Colectomy with ileorectal anastamosis is indicated in some patients if there is disabling symptoms, poor compliance with drug treatment, or a hugely dilated rectum [7].
Anorexia and poor GI absorption due to the chronic constipation and stool impaction can cause severe malnutrition. This important cause of malnutrition may go unnoticed because most patients prone to impaction are often unable to communicate particular problems [5]. Malnutrition has been shown to be associated with increased morbidity and mortality in the HD patients [1]. This case demonstrates that undiagnosis of indolent stool impaction can result in secondary megacolon and severe malnutrition. Although the causes of malnutrition are complex, a detailed history and physical examination remain the most important diagnostic tools in the assessment of HD patients with malnutrition.
Teaching point
Stool impaction is a reversible and remediable factor of malnutrition. To prevent inadvertent sequelae, physicians should keep alert to this common but easily overlooked issue in malnourished HD patients.
Notes
Supported by an educational grant from Fresenius Medical Care
References