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Abdominal computed tomography is normal
Medical expert of the article
Last reviewed: 04.07.2025
Normal anatomy
Sections of the abdominal organs cover the lower parts of the lungs, which continue to be visualized in the caudal direction in the posterior and lateral costophrenic sinuses. In the venous phase of contrast enhancement, the parenchyma of the liver and spleen usually has a homogeneous structure without focal changes. Only the branches of the portal vein and the round ligament can be seen. To assess the walls of the stomach, before the examination, the patient is given intravenous buscopan and a low-concentration KB solution to drink. The diaphragm, located between the thoracic and abdominal cavities, merges with the liver and spleen due to their equal density. If its section on the section passes in an oblique or perpendicular direction, the dome of the diaphragm can be seen as a thin structure.
The pancreas usually has a well-defined parenchyma and an irregular outline. The head and uncinate process of the pancreas descend quite far caudally. The left adrenal gland is often Y-shaped, while the right is sagittal or comma-shaped. Note the orifice of the celiac trunk and superior mesenteric artery, which branch off the abdominal aorta. Enlarged lymph nodes are often seen in this area.
Near the gallbladder, you can sometimes see a private volume effect due to the ascending colon. Normally, its walls are thin and well-defined, unlike the root of the mesentery of the small intestine. The duodenum differs from other loops of the small intestine only in its location. At this level, you should make sure that the edges of the kidneys are smooth and there is no shrinkage of the parenchyma. The fatty tissue allows for a clearer visualization of the rectus abdominis and oblique muscles in the abdominal wall.
After the bifurcation of the aorta (usually at the level of the L4 vertebral body), the common iliac arteries are located in front of the corresponding veins. Even more laterally, on the anterior surface of the lumbar muscles, both ureters are located. Together with the iliac bones, the gluteus medius muscles are visualized, in which there are sometimes areas of calcification after intramuscular injections.
The ureters pass posteriorly and approach laterally to the base of the bladder. Within the bladder, areas of different concentrations of urinary urea are found, which creates a boundary between fluids of different densities. The next page shows sections of the male pelvis. Note the prostate gland, seminal vesicles, spermatic cord, and root of the penis. The internal obturator and levator ani muscles are located on the sides of the anus. CT images of the male pelvis are located more caudal than those of the female pelvis.
Variations of normal anatomy
It is important for beginners to become familiar with the most common variations in normal anatomy that can cause errors in reading CT images. In some patients, the edge of the right lobe of the liver appears scalloped due to diaphragmatic depressions, which should not be mistaken for liver pathology. The walls of the unfilled stomach are thick and resemble a malignancy.
On ultrasound, it is possible to mistake the abnormal left renal vein for a retroaortic lymph node. Normally, the left renal vein runs between the superior mesenteric artery and the aorta. However, this vein can be located behind the aorta and directed to the inferior vena cava between the aorta and the spine. It is also common to see a duplication of the left renal vein, with one branch running in front of the aorta and the other behind the aorta.
Manifestations of the partial volume effect
When the wall of one organ is pushed into another, the cross-sectional image will look as if one organ is located inside the other. For example, the sigmoid colon may appear "inside" the bladder. Comparison of adjacent sections shows that only parts of these organs are represented in the image. A similar picture occurs when the right flexure (hepatic angle) of the colon is located "inside" the gallbladder.
Anatomy of the female pelvis
In the female pelvis, the size of the uterus and its position relative to the bladder vary considerably. The uterus may be located above or to the side of the bladder. The cervix and vagina are located between the bladder and rectum, while the ovaries are seen more laterally. Depending on age and phase of the menstrual cycle, follicles may be detected in the ovaries, which may be mistaken for cystic lesions).
Free fluid in the abdominal cavity (in case of ascites or bleeding) can be detected in the rectouterine pouch between the rectum and the uterus, as well as in the vesicouterine space. Normally, the lymph nodes in the inguinal region can reach 2 cm in diameter). The size of normal lymph nodes in the abdominal cavity usually does not exceed 1 cm. The hip joints cannot be examined in the soft tissue window. The heads of the femurs in the acetabulum are better analyzed in the bone window (not shown here). Evaluation of the structures in the bone window completes the examination of the abdominal cavity and pelvis.
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