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INTRODUCTION

Test Taking Tips

  • Questions regarding colorectal anatomy, physiology, and pathology are all too common on the ABSITE; while most subjects are fair game, common themes are tested. Comparing and contrasting ulcerative colitis and Crohn disease will always draw a question or two, while other benign conditions, such as volvulus and diverticulitis, will garner questions about nonoperative and operative management.

  • Colorectal cancer is a broad topic with many items that may be tested. Know the proto-oncogenes and tumor suppressor genes associated with the condition, as well as the eponymous diseases, which are risk factors or markers for the development of malignancy. It is also helpful to know the treatment of the different stages of colorectal cancer with regard to neoadjuvant and adjuvant chemotherapy, as well as radiotherapy.

ANATOMY AND PHYSIOLOGY

Where does the hindgut begin and end?

  • Hindgut begins at distal third of the transverse colon and extends to the rectum

The hindgut relies on which artery for its blood supply?

  • Inferior mesenteric artery

What are the white lines of Toldt?

  • The lateral peritoneal reflections of the ascending and descending colon

What parts of the gastrointestinal (GI) tract do not have a serosa?

  • Esophagus, middle, and distal rectum

What are the major anatomic differences between the small bowel and colon?

  • The small bowel is smooth, whereas the colon has fat appendages (appendices epiploicae), haustra, and taenia coli

What is the arterial blood supply to the rectum?

  • Proximal: superior hemorrhoidal artery (superior rectal artery) from the inferior mesenteric artery

  • Middle: middle hemorrhoidal artery (middle rectal artery) from the hypogastric artery (internal iliac artery)

  • Distal: inferior hemorrhoidal artery (inferior rectal artery) from the pudendal artery, which is a branch of hypogastric artery (internal iliac artery)

What is the venous drainage of the rectum?

  • Proximal: inferior mesenteric vein that joins the splenic vein to drain into the portal vein

  • Middle: iliac vein into the inferior vena cava

  • Distal: iliac vein into inferior vena cava

FIGURE 20-1

Arterial supply to the rectum and anal canal. (Reproduced with permission from Brunicardi FC, Andersen DK, Billiar TR, et al. Schwartz’s Principles of Surgery, 9th ed. New York, NY: McGraw Hill; 2010.)

What is the purpose of the colon?

  • Water, sodium, and bile salt absorption and stool storage

What is the main nutrient of a colonocyte?

  • Short-chain fatty acids (SCFAs) (butyrate)

How long is the rectum?

  • 12 to 15 cm

What are the approximate proximal and distal extents ...

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