Breast fed babies with hirschsprung's disease tend not to manifest as severe clinical features as infants fed artificial formulae. In severe cases there is likely to be a loss of subcutaneous tissue and failure to grow. The wasted extremeties and large, protruding abdomen may be confused with that of the malabsorption syndromes especially when diarrhoea is present. An assessment of the anal position on the perineum is important. A subtle, low - lying imperforate anus with an opening that is displaced in an anterior direction may also be a cause of constipation.
Rectal examination reveals a tight anus that is occasionally diagnosed as anal stenosis.
Diagnosis A rectal biopsy by the punch or suction method that finds absence of ganglion cells in the submucosa and the intermuscular nerve plexuses with or without an increased numbers of nerve fibres is the only conclusive means. Disadvantages of a rectal biopsy include bleeding, scarring and the need for general anesthesia. Because the ganglion cells normally diminish in number in the more distal rectum and the anal canal, biopsies should be taken no closer than 1 cm to the pectinate line. First time rectal examination and washouts before the study should be avoided because they may distort a low transition zone. An abrupt change in the calibre between the ganglionic and aganglionic section of bowel.