To accurately describe the locations of visible abnormalities, masses, and pain in a typical clinical write-up, the anterolateral abdomen is divided into nine regions by four imaginary planes: two verticals (midclavicular/ midinguinal) and two horizontal (transpyloric/intertu-bercular) planes (Fig. 1.1). The transpyloric plane corresponds to the midpoint between the umbilicus and xiphoid process, crossing the pylorus of the stomach at
the lower border of the first lumbar vertebra. The subcostal plane that passes across the costal margins and the upper border of the third lumbar vertebra may be used instead of the transpyloric plane. The lower horizontal plane, designated as the intertubercular line, traverses the anterior abdomen at the level of fifth lumbar vertebra, and connects the iliac tubercles on both sides. A second lower horizontal plane, the interspinous plane, may also be used, interconnecting the anterior superior iliac spines on both sides and running across the sacral promontory. Of the nine areas, the centrally placed zone is the umbilical region. This region surrounds the umbilicus and usually corresponds to the location of the jejunum, transverse part of the duodenum, terminal ileum, transverse colon, ureter and the greater curvature of the stomach.
The epigastrium is the upper middle part of the anterior abdomen between the umbilicus below and the costal arches and the xiphoid process above. It contains the stomach, left lobe of the liver, and part of the pancreatic head. The pubic region known as the hypogastrium de fines the zone immediately distal to the umbilical region and contains the ileum and sigmoid colon. The hypochondriac regions flank the epigastrium and are occupied on the right side by the liver, gallbladder, right colic flexure, descending duodenum, right kidney and suprarenal gland. On the left side these regions contain the spleen, left kidney and suprarenal gland, tail of the pancreas, left colic flexure, and fundus of the stomach. Most of the hypochondriac and parts of the epigastric regions are protected by the lower ribs. Areas immediately to the right and left of the umbilical region are designated as the right and left lumbar (lateral) regions, containing the ascending and descending colon, respectively. The right and left iliac regions surround the hypogastrium. The right iliac region contains the appendix and cecum, and the left iliac region corresponds to locations of the sigmoid colon and left ureter.
A simplified division of the anterolateral abdomen uses two imaginary planes that run through the umbilicus, one passing horizontally and the other vertically. The four quadrants separated by these planes divide the anterior abdomen into the right and left upper and lower quadrants.
In summary, the regions described above help medical practitioners to accurately describe the pathological processes associated with the anterior abdominal wall and to document the findings in the differential diagnosis. For example, periumbilical and hypogastric pain is felt during the initial stage of appendicitis, while pain in the right iliac region occurs at a later phase in this condition. Pancreatic or esophageal disorders produce pain that projects to the epigastrium.
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