Absolute Free USMLE Exam Practice for Comprehensive Preparation 

A neonate does not pass meconium until 48 hours after his birth. Two weeks later his mother reports that he has not been passing stool regularly. Anorectal manometry reveals increased internal anal sphincter pressure on rectal distention with a balloon. Radiographic studies reveal massive dilation of the colon proximal to the rectum. The findings in this case indicate a developmental abnormality of which of the following embryonic tissues? 

Laboratory results are as follows:

Hemoglobin – 9 g/dL

Mean corpuscular volume – 108 fl

MCHC – 33 g/dL

Mean corpuscular hemoglobin – 35 pg

A peripheral blood smear is obtained which reveals enlarged red blood cells and hypersegmented

neutrophils. These findings were most likely caused by

A 50-year-old male with AIDS develops a fever, headache and stiff neck. A sample of his cerebrospinal fluid reveals the presence of lymphocytes, glucose levels of 35 mg/dL and protein levels of 75 mg/dL. The test which would most likely confirm this patient’s diagnosis is the:

A patient presents to a physician with jaundice. Physical examination reveals a nodular, enlarged liver. CT of the abdomen shows a cirrhotic liver with a large mass. CT-guided biopsy of the mass demonstrates a malignant tumor derived from hepatic parenchymal cells. Infection with which of the following viruses would most likely be directly related to the development of this tumor?