Part 5: The abdomen
The trunk comprises the thorax, abdomen proper, pelvis, and back. (A portion of the back extends into the neck). The terms abdomen and abdominal cavity are frequently used to include the pelvis and pelvic cavity, respectively. The abdominal cavity proper is separated from the pelvic cavity below and behind by an arbitrary plane passing through the terminal lines of the bony pelvis. A considerable part of the abdominal cavity lies under cover of the thoracic bony cage. The abdominal cavity contains most of the organs of the digestive system, the spleen, the suprarenal glands, and the peritoneum. Certain organs may, at certain times, pass from the abdomen to the pelvis or vice versa.
A subdiaphragmatic thrust (applied quickly above the umbilicus) can force air from the lungs sufficiently to expel an obstructing object in the airway (Heimlich maneuver).
Examination of the abdomen
The classic methods of clinical examination are inspection, palpation, percussion, and auscultation. On inspection, the umbilicus, the rectus muscles, the respiratory movements, and the relative levels of the testes are noted. For palpation, the subject should be on an examining table and the examiner's hands should be warm. The flat of the hand is used. The abdominal muscles must be relaxed. On deep palpation, the following may sometimes be identified in normal subjects: pulsations of the abdominal aorta, the lumbar vertebrae, the lower pole of the right kidney, possibly the liver, and occasionally the spleen. Stroking the skin with a sharp point may induce contraction of the abdominal muscles (superficial abdominal reflex). Stroking the medial side of the thigh may induce elevation of the testis (cremasteric reflex). The superficial inguinal ring is examined with the subject erect by invaginating the scrotum with the little finger. The body of the uterus can be palpated bimanually, i.e., through the anterior abdominal wall and per vaginam. On percussion, a tympanitic note is obtained over the alimentary canal, whereas dullness is found over the liver, the spleen, and a full bladder. Auscultation is used chiefly to hear fetal heart sounds during pregnancy and bowel sounds in assessing intestinal peristalsis.
Radiological anatomy
An AP (antero-posterior) radiograph ("scout" or "KUB" film) of the abdomen shows the lower ribs, lumbar vertebrae, ilia, and sacro-iliac joints (see fig. 25-2). The shadow of the liver is usually evident, and it demarcates the domes of the diaphragm. The spleen, psoas muscles, and kidneys are often identifiable. Air in the fundus of the stomach and gas bubbles in the large intestine can usually be seen.
In addition to routine fluoroscopy and radiography, contrast media are frequently employed, e.g., a barium suspension (orally or by enema) for the alimentary canal (see figs. 27-2, 27-3, and 27-9) and organic iodides (orally, intravenously, or by injection into the bladder and ureters) to demarcate the calices of the kidney (see fig. 29-3). Radio-isotopic scanning (e.g., of the liver), computerized axial tomography, and ultrasound are being used with increasing frequency.