The right kidney is in intimate relationship to two segments of the gastrointestinal tract: the descending duodenum and the hepatic flexure of the colon. Figures 91 and 9-2 illustrate these relationships and the reflections of the posterior parietal peritoneum in the right flank. Virtually all of the right kidney is invested anteriorly by peritoneum except at two sites constituting its "bare areas":
1. Medially, the second portion of the duodenum de scends immediately in front of the right kidney. Here the peritoneum reflects to continue anterior to the duodenum and pancreas.
2. Inferiorly, the extraperitoneal colon courses obliquely over the lower pole of the kidney. This occurs precisely at its level between (a) the distal ascending colon and the posterior hepatic flexure, which is related superiorly to the deep inferior visceral surface of the liver, and (b) the anterior hepatic flexure as it crosses the descending duodenum; this segment marks the beginning of the transverse mesocolon and is related superiorly to the gallbladder.
A common variant exists in the extent of perito-nealization of the second portion of the duodenum. Frequently, the postapical segment of the duodenum remains intraperitoneal for several centimeters, even as it courses inferiorly, suspended by the lesser omentum. The point at which it penetrates the posterior parietal peritoneum to descend extraperitoneally as a straight segment is marked characteristically by a mild junctional flexure. An exaggerated form of this is seen as the "hammock" duodenum.
Because of the oblique position of the kidney along the lateral edge of the psoas muscle, its medial surface projects somewhat anterior to its lateral border. Thus, it can be appreciated that both anterior and medial displacement of the descending duodenum, distal to its postapical segment, would result from a right renal mass.
While some variation occasionally exists, the descending duodenum usually lies on a more posterior plane than the duodenojejunal junction at the ligament of Treitz. In a standard right lateral projection of an upper GI series, therefore, projection of the second duodenum anterior to the fourth (ascending) duodenum and duodenojejunal junction should be viewed with suspicion of a right renal mass.
Fig. 9—1. Frontal drawing emphasizing relationships of right kidney to descending duodenum and hepatic flexure of the colon by virtue of their peritoneal reflections.
The upper two-thirds of the right kidney are related to the right colon between its two flexures, whereas the lower pole is inframesocolic and is related laterally and anteriorly to the distal ascending colon.
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This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.