Organomegaly

Definitions for various organs

Hepatomegaly is enlargement of the liver. On medical imaging, the longitudinal axis exceeds 15.5 cm at the hepatic midline or 16.0 cm at the midclavicular line. At autopsy, liver weight above the upper limit of the standard reference range—1860 g in men and 1770 g in women—indicates hepatomegaly. Lymphadenopathy generally refers to lymph nodes measuring 10 mm or more. The renal pelvis is part of hydronephrosis grading; in adults, cutoff values for anteroposterior diameter range between 10 and 20 mm depending on the source, and about 13% of normal healthy adults have a transverse pelvic diameter over 10 mm. In fetuses, an anteroposterior diameter less than 4 mm up to 32 weeks of gestational age and less than 7 mm afterwards is considered normal. Prostatomegaly is defined as a prostate volume over 30 cm³. Dilation of the pulmonary artery is indicated by a diameter greater than 29 mm. Small intestine dilation is 2.5 cm on CT scans (mild 2.5–2.9 cm, moderate 3–4 cm, severe >4 cm) and 3 cm on abdominal X-rays due to geometric magnification. Small intestine wall thickening is 3–5 mm. Splenomegaly on imaging is a largest dimension over 11 cm or a craniocaudal height of 13 cm; moderate splenomegaly is 11–20 cm, severe greater than 20 cm. At autopsy, splenic weight above 230 g indicates splenomegaly. Thoracic aorta dilation is generally a diameter over 3.5 cm, with upper limits of the standard reference range varying: ascending aorta 3.3 cm in small young individuals to 4.3 cm in large elderly individuals; descending thoracic aorta 2.3 cm in small young individuals to 3.2 cm in large elderly individuals. Thoracic aortic aneurysm is defined as a diameter greater than 4.5 cm in the US and greater than 4.0 cm in Korea. Testicular enlargement is 5 cm long axis by 3 cm short axis. Enlarged tonsils measure 2.5 cm in length, 2.0 cm in width, and 1.2 cm in thickness. Megaureter is defined as a ureter diameter of 6 or 7 mm. Urinary bladder wall thickening is 3–5 mm thick, and less than 3 mm when well distended.