Medical Term Glossary
Plain-language explanations of the medical terms that appear on CT, MRI and X-ray reports — what each one means, when it matters, and what to ask your doctor.
A
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Abdominal aortic aneurysm
An outward bulge in the wall of the aorta, the body's main artery, where it runs through the abdomen. Radiologists measure the aorta's width on every abdominal CT or MRI and note whether it is normal, and this term is often searched even when a report says no aneurysm is present.
Also: AAA, abdominal aorta aneurysm, aorta ballooning
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Accessory spleen (splenule)
A small extra piece of spleen tissue, separate from the main spleen but built the same way and just as harmless. It forms before birth in roughly one in ten people and is usually found by chance near the spleen, though it can occasionally be mistaken for a lymph node or tumor.
Also: ectopic splenic tissue, extra spleen, spleniculus
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Adrenal adenoma
A common, non-cancerous growth in the adrenal gland, the small hormone-producing organ that sits atop each kidney. It is one of the most frequent incidental findings on abdominal CT and MRI scans, and in the large majority of cases it is harmless and does not affect hormone levels.
Also: adrenal cortical adenoma, adrenal gland adenoma, adrenal incidentaloma
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Adrenal gland
A small, triangular hormone-producing organ sitting on top of each kidney. It releases stress hormones such as cortisol and adrenaline, along with chemicals that help the body manage salt, water, and blood pressure. Small spots found here by chance on a scan are extremely common and the vast majority turn out to be harmless.
Also: adrenal, adrenals, gland above the kidney
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Aortic dissection
A tear in the inner lining of the aorta, the body's main artery, that lets blood force its way between the layers of the vessel wall and split them apart. It is a medical emergency that needs immediate hospital care, even when a scan describes it as limited, stable, or chronic.
Also: Stanford type A, Stanford type B, aortic tear
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Appendicitis
Inflammation of the appendix, a small pouch attached to the large intestine, usually caused by a blockage that lets bacteria multiply inside it. It is one of the most common reasons for emergency abdominal CT scans and typically needs prompt treatment to prevent rupture.
Also: acute appendicitis, appendix infection, appendix inflammation
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Ascites
Extra fluid that has collected inside the belly, in the space surrounding the bowel and organs. A small amount can be normal in some situations, but larger collections almost always point to a problem with the liver, heart, kidneys, or the lining of the abdomen itself. The cause matters far more than the fluid.
Also: abdominal effusion, abdominal fluid, fluid build-up in the belly
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Atherosclerosis (vascular calcification)
Hardening and narrowing of artery walls from years of fatty and calcium deposits building up inside them, often spotted incidentally while scanning the abdomen for something else. It's an extremely common part of aging and reflects cumulative cardiovascular risk rather than an urgent problem in the abdomen itself.
Also: aortic calcification, arterial calcification, arteriosclerosis
B
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Biliary dilatation
A widening of the small tubes that carry bile from the liver to the bowel. It usually means something downstream is slowing or blocking the flow — a stone, a narrowing, an inflamed pancreas, or, less often, a mass. The location and degree of the widening tell the medical team where to look next.
Also: bile duct dilation, biliary dilation, biliary tree dilation
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Biliary sludge
Thickened, gritty bile that settles in the gallbladder instead of flowing smoothly, often seen as layering material on ultrasound, CT, or MRI. It is usually a temporary, benign finding linked to fasting, pregnancy, or illness, and it often clears on its own without treatment.
Also: bile sludge, biliary sediment, gallbladder sludge
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Bosniak classification
A grading scale radiologists use to sort kidney cysts by how likely they are to be cancer, based on their appearance on CT or MRI. Categories run from I (simple, harmless) through II, IIF, III, up to IV (features that raise concern). It guides whether a cyst is ignored, watched, or investigated.
Also: bosniak 2f, bosniak category, bosniak cyst grade
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Bowel obstruction
A blockage that stops food, fluid, and gas from moving through the intestines as they normally would. The gut above the block stretches and fills with fluid and air, which is what shows up on a scan. It is almost always a problem that needs prompt medical attention, sometimes urgent surgery.
Also: blocked bowel, blocked intestine, gut blockage
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Bowel perforation
A hole that has opened through the full thickness of the intestinal or stomach wall, letting gas and gut contents leak into the abdominal cavity. It is one of the true emergencies in imaging, usually treated with immediate surgery, and radiologists look for it urgently whenever free air appears on a scan.
Also: gastrointestinal perforation, gut perforation, intestinal perforation
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Cecum
The first, pouch-like part of the large bowel, sitting low in the right side of the belly where the small intestine empties in. The appendix hangs from it. Its name comes from a word meaning blind, as it is a dead-end pouch. Reports often name it to locate a finding in the lower right belly.
Also: blind pouch of colon, caecum, cecal pouch
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Cholecystectomy
Surgical removal of the gallbladder, most often done to treat gallstones or gallbladder inflammation. When a scan report mentions this term, it usually means the gallbladder is absent because it was already removed in a prior operation, which is a normal and expected finding rather than a new problem.
Also: gallbladder removal, gallbladder removal surgery, gallbladder resection
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Coprostasis (stool retention)
A buildup of hardened stool sitting in the colon, most often the result of slow bowel transit, low fiber intake, or reduced mobility. It shows up clearly on CT as a colon packed with stool and gas, and is usually a benign, manageable finding rather than a sign of serious disease.
Also: colonic stool loading, constipation on CT, fecal loading
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Diverticulitis
Inflammation or infection of one of the small pouches that can form in the wall of the colon. It typically causes pain in the lower-left abdomen, often with fever. CT is the usual way to confirm it and to check for complications like an abscess. Most mild cases settle with treatment.
Also: acute diverticulitis, colonic diverticulitis, diverticular disease
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Diverticulosis
Small pouches that bulge outward from the wall of the large intestine, most often in the lower-left part. They are extremely common after middle age, usually cause no symptoms, and are typically found by chance on a scan or colonoscopy. They only become a concern if one of the pouches becomes inflamed or bleeds.
Also: bowel pouches, colon pouches, colonic diverticulosis
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Duodenum
The first, C-shaped part of the small intestine, just past the stomach. It receives food from the stomach and mixes it with juices from the pancreas and gallbladder to start digestion. Its name comes from a word for twelve fingers, its rough length. Reports often name it to locate a finding in the upper belly.
Also: C-loop of small bowel, duodenal loop, duodenal segment
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Fat stranding
Wispy, hazy streaks seen within a fat layer on a CT scan, replacing its normally smooth, dark appearance. It is a sign that something nearby — an organ, the bowel wall, an appendix — is inflamed or irritated, and it points radiologists toward the source rather than being a diagnosis on its own.
Also: fat haziness, haziness in the fat, inflammatory fat stranding
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Focal nodular hyperplasia (FNH)
A benign, non-cancerous growth of normal liver cells that forms a well-defined lump within otherwise healthy liver tissue. It is the second most common benign liver lesion, occurs mostly in women of childbearing age, and does not turn into cancer or usually require treatment.
Also: FNH, benign liver nodule, focal nodular hyperplasia liver lesion
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Gallbladder
A small pear-shaped sac tucked under the liver that stores and concentrates bile, the greenish fluid the liver makes to help break down fats. It releases that bile into the small intestine after a fatty meal. People can live normally without it if it has to be removed, which is one of the most common abdominal surgeries.
Also: bile sac, bile storage pouch, biliary sac
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Gallstones
Small, hardened deposits that form inside the gallbladder — the little pear-shaped sac that stores bile beneath the liver. Many people have them without ever knowing, and a quiet stone often needs no treatment. They only become a medical problem when one moves, blocks a duct, or sets off inflammation.
Also: biliary stones, cholecystolithiasis, cholelithiasis
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Gastric
Anything to do with the stomach. It is simply the medical adjective for 'relating to the stomach', from the Greek word for stomach. On its own it carries no good or bad meaning — it just tells you which organ a finding involves. The noun attached to it, like wall or folds, is what actually matters.
Also: of the stomach, pertaining to the stomach, relating to the stomach
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Hepatic cyst
A small, fluid-filled pocket sitting inside the liver. The vast majority are harmless, present from birth, and stay quiet for life. Many people have one without ever knowing — they tend to be found by chance on a scan ordered for something completely unrelated, and they rarely cause symptoms.
Also: benign liver cyst, biliary cyst, cyst in the liver
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Hepatic flexure
The sharp bend in the large bowel in the upper right belly, just under the liver, where the colon turns from heading up to running across. Hepatic means relating to the liver, its near neighbour. Reports often name it to locate a finding at this corner of the colon.
Also: colon bend near liver, hepatic colonic flexure, right colic flexure
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Hepatic hemangioma
A benign tangle of blood vessels growing within the liver, the most common noncancerous liver growth found on imaging. It is usually discovered by accident, causes no symptoms, and does not turn into cancer or need treatment in the vast majority of cases.
Also: benign liver lesion, cavernous hemangioma of the liver, hemangioma liver lesion
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Hepatic steatosis
Extra fat stored inside the cells of the liver. It is very common, often has no symptoms, and is usually picked up by chance on imaging done for other reasons. The amount of fat and the reason behind it — diet, weight, alcohol, or certain medications — guide how much it matters.
Also: MASLD, NAFLD, fat in the liver
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Hepatomegaly
An enlarged liver, measuring larger than the expected size range for the imaging test used. It's a descriptive finding rather than a diagnosis on its own, and the underlying cause — ranging from fatty liver to infection to heart or blood conditions — is what actually determines what happens next.
Also: big liver, enlarged hepatic size, enlarged liver
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Hiatal hernia
Part of the stomach slipping upward through the diaphragm into the chest cavity, through the same opening the esophagus normally passes through. It is a very common finding, often unrelated to any symptoms, and is one of the leading causes of acid reflux and heartburn.
Also: diaphragmatic hernia, esophageal hiatal hernia, hiatus hernia
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Hydronephrosis
A swelling of one or both kidneys caused by urine that cannot drain away properly. The backed-up fluid stretches the kidney's collecting system, which shows up clearly on imaging. The cause matters more than the swelling itself — kidney stones, narrowed tubes, and an enlarged prostate are typical reasons.
Also: dilated renal pelvis, kidney backup, kidney swelling
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Hydroureter
Abnormal widening of the tube that carries urine from the kidney to the bladder. It is almost always seen together with a swollen kidney, and together the two findings point to something blocking or slowing the normal flow of urine somewhere along the urinary tract.
Also: dilated ureter, distended ureter, ureter widening
I
J
K
P
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Pancreatic duct dilatation
Widening of the main channel that carries digestive enzymes from the pancreas into the small intestine, seen on CT or MRI. It is a sign that something is partly blocking or slowing flow through the duct, and it prompts a closer look to find the cause.
Also: PD dilatation, dilated pancreatic duct, main pancreatic duct dilatation
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Pancreatic mass
An area of abnormal tissue growth within the pancreas, seen as a distinct lump on CT or MRI. It can range from a fluid-filled cyst to a solid growth, and while some causes are benign, this finding is taken seriously and usually prompts further testing to determine what it is.
Also: mass in the pancreas, pancreas mass, pancreatic growth
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Pancreatitis
Swelling and irritation of the pancreas, the organ behind the stomach that makes digestive enzymes and insulin. It causes sudden, severe abdominal pain and usually needs prompt medical care. Most cases improve with treatment, though severe or repeated episodes can cause lasting damage.
Also: acute pancreatitis, chronic pancreatitis, inflamed pancreas
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Pneumoperitoneum (free air)
Air sitting inside the belly cavity where there should be none. Normally air stays inside the stomach and intestines; finding it loose in the surrounding space usually means a hole somewhere in the gut wall has let it escape. It is almost always treated urgently because the underlying leak needs prompt attention.
Also: free abdominal air, free air, free air in the belly
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Psoas muscle
A long, deep muscle on each side of the lower spine that runs down into the top of the thigh. It is a main hip flexor, lifting your knee toward your chest when you walk or climb stairs. Reports often name it as a landmark in the lower belly or to confirm it looks symmetric and normal.
Also: hip flexor, iliopsoas, psoas
R
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Rectum
The final straight section of the large bowel, sitting low in the pelvis just before the anus. It holds stool until you are ready to go, then signals the urge to pass it. Reports often name it to locate a finding in the lowest part of the bowel or to confirm it looks normal.
Also: back passage, final bowel section, lower bowel end
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Renal cell carcinoma
The most common type of kidney cancer in adults, arising from the cells lining the kidney's tiny filtering tubes. It is often found by chance on a scan done for an unrelated reason, and many cases are caught early, at a stage when they are highly treatable with surgery.
Also: RCC, clear cell renal carcinoma, hypernephroma
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Renal cyst
A small, fluid-filled sac inside the kidney. Most are harmless, develop quietly with age, and are picked up by chance on a scan done for something else. The radiologist's job is to tell the simple, benign kind apart from the rare more complex variety that needs a closer look — and most of the time it is the simple kind.
Also: benign kidney cyst, cyst on the kidney, fluid-filled kidney lesion
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Renal mass
An area in the kidney that looks different from the surrounding normal tissue and cannot yet be labeled clearly benign or cancerous from imaging alone. It is a placeholder description used until further scans or a biopsy narrow down what the abnormal area actually is.
Also: indeterminate kidney lesion, kidney growth, kidney lesion
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Sigmoid colon
The S-shaped final loop of the large bowel in the lower left side of the belly, just before the rectum. It stores formed stool until it is ready to pass. Its name comes from the Greek letter sigma because of its curve. Reports often name it to locate a finding in this part of the colon.
Also: S-shaped colon, pelvic colon, sigmoid
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Splenectomy
Surgical removal of the spleen, most often performed after trauma, for certain blood disorders, or during cancer treatment. When a scan report mentions this term, it usually means the spleen is absent because it was already removed, a normal and expected finding rather than a new problem.
Also: prior splenectomy, spleen removal, spleen removal surgery
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Splenomegaly
An enlarged spleen — the small, fist-sized organ tucked under the ribs on the left side. It is a sign, not a diagnosis: the spleen grows in response to many different things, from a recent viral infection to long-standing liver disease or a blood disorder. The reason behind the enlargement is what matters.
Also: big spleen, enlarged spleen, spleen enlargement
U
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Umbilical hernia
A bulge that forms when a small portion of fatty tissue or bowel pushes through a weak spot in the abdominal muscles near the belly button. It's common in adults, especially with pregnancy or extra weight, and is often noticed as a soft lump rather than found only by imaging.
Also: belly button hernia, navel hernia, paraumbilical hernia
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Ureter
A thin muscular tube, one on each side, that carries urine from a kidney down to the bladder. Gentle squeezing waves push the urine along. There are two, one per kidney. Reports often name the ureters to confirm they look normal or to locate a finding such as a stone along their path.
Also: kidney tube, renal drainage tube, ureteric tube
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Ureteral stent
A thin, flexible tube placed inside the ureter to keep urine flowing from the kidney to the bladder when the tube is blocked or at risk of narrowing. It shows up on CT as a curling line, one end coiled in the kidney and the other in the bladder.
Also: DJ stent, JJ stent, double-J stent
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