This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Urology, Subject name: Surgery
In which of the following conditions acquired (secondary) megacolon seen? 
Select and explain. 
A. Fissure in-ano, B. Complete absence of parasympathetic ganglion cells, C. Absence of sympathetic ganglion cells, D. Rectal malignancy
D: Rectal malignancy
Answer: D: Rectal malignancy 
Explanation: Acquired megacolon - marked dilatation of the entire colon or its segment due to acquired causes(rectum and sigmoid colon are dilated). Normal ganglions are present in all levels. It is seen in children with faulty toilet training resulting in chronic bowel dilatation. Causes include: *Obstructive- tumours (rectal malignancy), post inflammatory strictures *Endocrine- myxoedema, cretinism *CNS disorders- spina bifida, paraplegia, parkinsonism *Psychogenic- emotional disturbances, psychiatric disorders *Chagas' disease d/t infection with Trypanosoma cruzi- acquired loss of ganglion cells Congenital absence of ganglion cells in the bowel wall results in congenital megacolon(Hirschsprung's disease). Fissure in ano causes anal sphincter spasm, but does not result in megacolon. Reference : page 580 Textbook of pathology Harshmohan 6th edition