Abdomen Flashcards
Normal supine abdomen.
This is the “scout” film of the abdomen, the one that gives you a general idea of the bowel gas pattern and allows you to search for abnormal calcifications and detect organomegaly. There is usually a small amount of air in about two or three loops of nondilated small bowel (solid black arrow).There will almost always be air in the stomach (dotted black arrow)and in the rectosigmoid colon (solid white arrow).Depending on the amount of fat around the visceral organs, the outlines of these organs may be partially visible on conventional radiographs. The psoas muscles are outlined by fat (dotted white arrows),making them visible on this image.
Normal prone abdomen.
In the prone position, the ascending and descending colon, as well as the rectosigmoid colon, all of which are posterior structures, are the highest parts of the large bowel and thus most likely to fill with air. There is air in the S-shaped rectosigmoid colon (black arrow).Air can also be seen throughout the remainder of the colon (white arrows).
Normal colonic distension.
The diameter of the colon on a barium enema study is the size to which the colon can normally distend (white arrows),beyond which it would be considered dilated. This patient has had a double-contrast barium enema examination in which both air and barium were instilled as contrast agents. The combination of air and barium allows for excellent visualization of the mucosal surface of the colon.
Appearance of stool.
Stool is recognizable by the multiple, small bubbles of gas present within a semisolid-appearing soft tissue density (white circle).Stool marks the location of the large bowel and can help in identification of individual loops of bowel on conventional radiographs. This patient has a markedly dilated sigmoid colon due to chronic constipation.
Aerophagia.
Virtually all bowel gas comes from swallowed air. Swallowing large quantities of air may produce a picture called aerophagia,characterized by numerous polygon- shaped, air-containing loops of bowel, none of which is dilated (white circle).
Normal upright abdomen.
There are two things to look for on an upright view of the abdomen: air–fluid levels and free intraperitoneal air. Normally, there is an air–fluid level in the stomach (solid black arrow).There may be short air–fluid levels in a few nondilated loops of small bowel (black circle).There are usually very few or no air–fluid levels in the colon. Free air, if present, should be visible just below the hemidiaphragm (dotted black arrow)and would be easier to recognize on the right than on the left.
Location of large bowel.
The large bowel usually occupies the periphery of the abdomen. The small bowel is located more centrally. Here, the large bowel (black arrows)contains a normal amount of air. The liver occupies the right upper quadrant and normally displaces all bowel from this area.
Normal large bowel haustral markings.
Most haustral markings in the colon do not traverse the entire lumen to extend from one wall to the opposite wall (white arrows).This appearance is unlike that of the valvulae conniventes in the small bowel, which do appear to traverse the entire lumen. The haustral markings are also spaced more widely apart than the valvulae of the small bowel (
Normal small bowel valvulae.
Markings representing the valvulae typically extend across the lumen of the small bowel to reach from one wall to the other. In addition, the valvulae are spaced much closer together than the haustra of the large bowel, even when the small bowel is dilated. The white arrowspoint to two valvulae that traverse the entire lumen in this close-up of dilated small bowel.
Normal lateral view of the rectum.
Frequently, patients are unable to lie prone because of their physical condition (e.g., recent surgery, severe abdominal pain). These patients can turn onto their left side and have a lateral view of the rectum exposed, with a vertical beam used to substitute for the prone radiograph. The lateral view of the rectum will usually demonstrate the presence or absence of air in the rectum and/or sigmoid colon (black arrow).
Normal left lateral decubitus view of the abdomen.
For a left lateral decubitus view, patients lie on their left side on the examining table, and an exposure is made with a horizontal x-ray beam (parallel to the floor). This is done so that any “free air” will distribute itself at the highest part of the abdominal cavity, which will be the patient’s right side. Free air, if present, should be easily visible as a black crescent over the outside edge of the liver (white arrows),a location in which there is normally no bowel gas present. In this photo, the patient’s head is positioned toward your right, with the feet pointing toward your left.
Phleboliths.
Phleboliths are small, rounded calcifications that represent calcified venous thrombi that occur with increasing age, most often in the pelvic veins of women. They clas- sically have a lucent center (white arrow).In the pelvic veins, they are considered incidental and nonpathologic calcifications, but they can be confused with ureteral calculi.
Calcified rib cartilages.
Calcifications of the rib cartilage (white circle)occur with advancing age, and, though they are not true abdominal calcifications, they can sometimes be con- fused for calculi when they superimpose on the kidney or the region of the gallbladder. Calcified cartilage tends to have an amorphous, mottled appearance. Calcified rib cartilages occur along an arc corresponding to the sweep of the anterior ribs as they turn back toward the sternum.
Riedel lobe of the liver.
Occasionally, a tongue-like projection of the right lobe of the liver may extend to the iliac crest, especially in women. This is called a Riedel lobeand is normal (black arrows).Conventional radiography is a notoriously poor tool for estimating the size of the liver. CT, MRI, and US give a more accurate picture of liver size.
Hepatomegaly.
Sometimes the liver can become so enlarged that it will be obvious even on conventional radiographs. Conventional radiographs may suggest an enlarged liver if there is displacement of all bowel loops from the right upper quadrant down to the iliac crest and across the midline (black arrows),such as in this patient with cirrhosis.
Splenomegaly.
The spleen is about 12 cm in length and usually does not project below the 12thposterior rib. If the spleen (white arrows)projects well below the 12thposterior rib (black arrow)and/or displaces the stomach bubble toward or across the midline, it is probably enlarged, as it is in this patient with leukemia.
Position of the kidneys.
This is one image from an intravenous urogram,also known as an intravenous pyelogram(IVP). For an IVP, the patient is given an intravenous injection of iodinated contrast dye, which is excreted by the kidneys. Both kidney outlines (solid white arrows),the ureters (solid black arrows),and the urinary bladder (dotted black arrow)can be seen. Using IVPs, other images of the kidneys, including oblique views, were often obtained to visualize the entire contour of the kidney. IVPs have largely been replaced by CT scans in the form of CT urograms. The liver (dotted white arrow)normally depresses the right kidney more inferiorly than the left kidney.
Enlarged kidney.
Soft tissue masses or organomegaly can be diagnosed on the basis of a conventional radiograph, either by visualizing the edge of the mass if there is fat or air surrounding it or by displacement of bowel. A,On this conventional radiograph, there is a soft tissue mass in the left upper quadrant (white arrows)that is displacing bowel to the right (black arrow).B,A coronal reformatted CT scan of the same patient demonstrates a large renal cyst (white arrows)arising from the left kidney (black arrow),displacing it and surrounding bowel. The spleen (S) is being compressed by the cyst.
Normal urinary bladder.
Close-up of the pelvis demonstrates enough perivesical fat present to make the outline of the urinary bladder visible (white arrows).In men, the sigmoid colon usually occupies the space just above the bladder (black arrow).In women, the soft tissue above the bladder may be either the uterus or the sigmoid colon.
Distended urinary bladder and enlarged uterus
A,The distended bladder (labeled B) is a soft tissue mass that ascends from the pelvis into the lower abdomen, displacing the bowel into the mid abdomen (black arrows).This image was obtained from a 72-year-old man with bladder outlet obstruction due to benign prostatic hypertrophy. B,The uterus (labeled U) is slightly enlarged. It can be distinguished from the bladder because there is a fat plane (white arrows)between it and the urinary bladder (labeled B) below it.
Normal liver anatomy.
The ligamentum teres (dotted black arrow) divides the left lobe of the liver into a medial (M) and lateral (L) segment with the larger right (R) lobe lying more posterior. The portal vein (PV) lies just posterior to the hepatic artery (solid black arrow). The splenic artery (solid white arrow) follows the path of the pancreas (P) towards the spleen (S). The inferior vena cava (IVC) lies to the right of the aorta (A).
Bare area of the liver.
The bare area of the liver (white arrows) has no peritoneal covering but is affixed directly to the undersurface of the diaphragm. As such, it will be impossible for ascitic fluid in the peritoneal cavity (P) to insert itself between the liver and the lung in this area, which will be important for differentiating pleural effusion from ascites (see Chapter 20). Ant, Ante- rior; Post, posterior.
Normal pancreas.
A, Body of pancreas (thick white arrow) and splenic artery (thin white arrow). Additionally well visualized are both adrenal glands (dotted white arrows) and gallbladder (black arrow). B, Normal head of pancreas (solid white arrow). Because the pancreas is oriented obliquely, the entire organ is not seen on any one axial image of the upper abdomen. The tail is most superior and the body and then head are usually visualized on successively more inferior slices.
Normal kidneys.
The kidneys (K) lie in the renal fossae bilaterally. The normal renal pelvis, containing fat, occupies the central portion of the kidneys (dotted black arrows). The right renal artery (solid black arrow) runs posterior to the inferior vena cava (IVC). The left renal vein (dotted white arrow) here lies anterior to the left renal artery (solid white arrow). A, Abdominal aorta.
Renal cortex and medulla, computed tomography.
The kidneys are the primary organ by which iodinated contrast is excreted. The kidneys will appear slightly different depending on the time the scan is performed following the injection. About 70 to 100 seconds after the injection, a nephrographic (nephrogram) phase, such as this, will demonstrate the corticomedullary junction between the outer, brighter cortex (solid black arrows) and the inner, less-dense medulla(dotted black arrows).
Normal bowel.
Contrast fills a nondilated lumen (less than 2.5 cm). The small bowel wall is so thin as to normally appear almost invisible (white arrows). The terminal ileum can be rec- ognized by the fat-containing “lips” of the ileocecal valve outlined with contrast (black arrows).
Normal bladder.
The urinary bladder (B) contains unopacified urine in this early image of a contrast-enhanced computed tomography scan of the pelvis. The bladder wall (solid white arrows) is thin and of equal thickness around the circumference of the bladder. The rectum lies pos- terior to the bladder (dotted white arrow).
Sentinel loops from pancreatitis.
A single, persistently dilated loop of small bowel is seen in the left upper quadrant (white arrows) on both the supine (A) and prone (B) radiographs of the abdomen representing a sentinel loop or localized ileus. A localized ileus is called a sentinel loop because it often signals the presence of an adjacent irritative or inflammatory process. This patient had acute pancreatitis.
Pancreatitis producing focal bowel dilatation.
Although the cause of a sentinel loop can usually only be inferred from conventional radiographs, computed tomography (CT) scans can depict the underlying abnormality producing the bowel irritation. In this contrast-enhanced, axial CT scan of the upper abdomen with oral contrast, the pancreas is inflamed, enlarged, and edematous(white arrows), and there is infiltration of the peripancreatic fat. This can affect peristalsis in adjacent loops of small bowel (SB) and lead to dilatation of the loops.
Generalized adynamic ileus, supine
(A) and upright abdomen (B). There are dilated loops of large (solid white arrows) and small (dotted white arrows) bowel with gas seen down to and
including the rectum (solid black arrows). The patient had absent bowel sounds and had undergone colon surgery the day before.
Small bowel obstruction from inguinal hernia.
A, The scout image from a computed tomography (CT) scan of the abdomen reveals dilated loops of small bowel (solid black arrow) caused by a left inguinal hernia (white circle). Loops of bowel should normally not be present in the scrotum. B, Coronal-reformatted CT scan on another patient shows multiple fluid-filled and dilated loops of small bowel (solid white arrows) from an inguinal hernia (white circle) containing another dilated loop of small bowel (dotted white arrow).
Step-ladder appearance of obstructed small bowel.
As they begin to dilate, small bowel loops stack up, forming a step-ladder appearance usually beginning in the left upper quadrant and proceeding—depending on how distal the small bowel obstruction is—to the right lower quadrant (black arrows). The more proximal the small bowel obstruction (e.g. proximal jejunum), the fewer the dilated loops there will be; the more distal the obstruction (e.g., at the ileoce- cal valve), the greater the number of dilated small bowel loops. This was a distal small bowel obstruc- tion caused by a carcinoma of the colon, which obstructed the ileocecal valve.
Mechanical small bowel obstruction.
Even though there is still a small amount of air in the right colon (white arrow), the overall bowel gas pattern is one of disproportionate dilation of multiple loops of small bowel (black arrows) consistent with a mechanical small bowel obstruction. The obstruction was secondary to adhesions.
Partial small bowel obstruction, supine (A) and upright (B).
A partial or incomplete mechanical small bowel obstruction is one that allows some gas to pass the point of obstruction, possibly on an intermittent basis. This can lead to a confusing picture because gas may pass into the colon (solid black arrows) and be visible long after the large bowel would be expected to be devoid of gas. The important observation is that the small bowel is disproportionately dilated (dotted white arrows) compared with the large bowel, a finding suggestive of small bowel obstruction. Partial or incomplete small bowel obstructions occur more often in patients in whom adhesions are the etiologic factors. Notice the clips (solid white arrows) attesting to prior surgery.
Partial small bowel obstruction.
Coronal-reformatted computed tomography scan with oral contrast shows dilated and contrast-containing loops of small bowel (solid white arrows). Although there is still air in the collapsed colon (dotted white arrows), the disproportionate dilatation of small bowel identifies this as a small bowel obstruction.
Small bowel obstruction due to Spigelian hernia.
A Spigelian hernia is one that occurs at the lateral edge of the rectus abdominis muscle at the semilunar line. This patient has a transition point (solid white arrow) as the small bowel enters the hernia (dotted white arrow). More proximally, there are multiple dilated loops of small bowel (solid black arrows), indicating obstruction. The colon is beyond the point of obstruction and is collapsed (dotted black arrow).
Small bowel obstruction, computed tomography with oral and intravenous (IV) contrast.
There are multiple fluid- and contrast-filled, dilated loops of small bowel (solid black arrows) although the colon is collapsed (white arrows), indicating a small bowel obstruction. Bowel wall enhancement, or lack thereof, may be obscured by oral contrast, a drawback to the use of oral contrast. Incidentally noted is a right renal cyst (dotted black arrow).
Small bowel feces sign.
There is air mixed with debris and old oral contrast in a dilated loop of small bowel (solid white arrows). There are proximal, fluid-containing, dilated loops of small bowel (dotted white arrows). The patient had a computed tomography scan with oral contrast several days earlier for abdominal pain and returned for this noncontrast scan when symptoms per- sisted. Intestinal debris and fluid may accumulate in the loop, usually just proximal to a small bowel obstruction, and present with this finding, which resembles fecal material in the colon.
Closed-loop obstruction, computed tomography.
A loop of small bowel is obstructed twice at the same point of twist (solid white arrow) producing a closed loop (CL). No oral contrast enters the closed loop but is present in a more proximal loop of small bowel (dotted white arrow). Closed-loop obstructions are important because of their higher incidence of bowel necrosis from strangulation of the bowel.
Bowel necrosis, contrast-enhanced computed tomography (CT).
A dilated loop of small bowel demonstrates normal enhancement of the wall (white arrow) on this coronal reformat of a contrast-enhanced CT, whereas more distal, dilated loops of small bowel show no wall enhancement (black circle). This is an indication of vascular compromise of the distal loops with bowel necrosis.
Mechanical large bowel obstruction.
The entire colon is dilated (dotted white arrows) to a cut-off point in the distal descending colon (solid white arrow), the site of this patient’s obstructing carcinoma of the colon. Some gas has passed backward through an incompetent ileocecal valve and outlines a dilated ileum (solid black arrow). Notice that the large bowel is disproportionately dilated compared with the small bowel, a finding of large bowel obstruction.
Large bowel obstruction masquerading as a small bowel obstruction.
There are air-filled and dilated loops of small bowel (solid white arrows) in this patient who actually had a mechanical large bowel obstruction from a carcinoma of the middescending colon. The pressure in the colon was sufficient to open the ileocecal valve, which then allowed much of the gas in the colon to decompress backward into the small bowel. The cecum still contains air (dotted white arrow) and is dilated, a clue that this is really a large bowel obstruction. Abdominal computed tomography can resolve the question of whether the large or small bowel is obstructed.
Large bowel obstruction from carcinoma of the colon.
This coronal- reformatted CT scan of the abdomen and pelvis shows dilated cecum containing stool (dotted white arrow) and large bowel (LB) to the level of the distal descending colon where a large soft tissue mass is identified (solid white arrow). This mass was an adenocarcinoma of the colon and was surgically removed.
Sigmoid volvulus, supine abdomen.
There is a massively dilated sigmoid colon(solid white line) that is twisted upon itself in the pelvis (black arrow). The dilated sigmoid has acoffee-bean shape. Since the point of obstruction is in the distal colon, there is air and stool in the more proximal portion of the colon (white arrows). Volvulus can produce massively dilated loops of sigmoid colon.
Ogilvie syndrome.
Ogilvie syndrome (acute intestinal pseudoobstruction) may occur in older adults who are usually already hospitalized or on chronic bed rest. Drugs with anticho- linergic effects may cause or exacerbate the condition. The syndrome is characterized by a loss of peristalsis, resulting in sometimes massive dilatation of the entire colon resembling a large bowel obstruction, as in this patient. Treatment is pharmacologic stimulation of the bowel
Free air beneath the diaphragm.
There are thin crescents of air beneath both the right (solid white arrow)and left (dotted white arrow)hemidiaphragms representing free intraperito- neal air. The patient had undergone abdominal surgery 3 days earlier. Free air can remain for up to 7 days after surgery in an adult, but serial studies should demonstrate a progressively decreasing amount of air.
Large amount of free air.
Upright view of the chest demonstrates a large amount of free air (A) beneath each hemidiaphragm (white arrows). The top of the liver (black arrow)is made visible by the air above it. The patient had a perforated gastric ulcer.
Free air seen on CT scan of the abdomen.
Axial CT scan of the upper abdomen performed with the patient supine shows free air anteriorly (white arrows). The air is not contained within any bowel. Free intraperitoneal air will normally rise to the highest point of the abdomen, which in the supine position is beneath the anterior abdominal wall.
Normal left hemidiaphragm (A) and free air under hemidiaphragm (B).
Close-up views of the left upper quadrant demonstrate the difficulty in recognizing free air beneath the left hemidiaphragm because of the normal location of gas-containing structures such as the stomach (S) and splenic flexure (SF). There is no free air in (A),but the other patient (B)does have a crescent of free air (white arrows).It is easier to recognize free air beneath the right hemidiaphragm because there is usually no air above the liver on the right side.
Left lateral decubitus view showing free air.
Close-up of the right upper quadrant in a patient lying on the left side in the left lateral decubitus position shows a crescent of air (dotted white arrows)above the outer edge of the liver (black arrow),beneath the right hemidiaphragm (solid white arrow).The head/foot orientation of the patient is indicated. If the patient is unable to stand or sit up for an upright view of the abdomen, a left lateral decubitus view with a horizontal beam can substitute.
Rigler sign.
When air fills the peritoneal cavity, both sides of the bowel wall will be outlined by air (white arrows)making the wall of the bowel visible as a discrete line. This is known as Rigler
signand indicates the presence of a pneumoperitoneum. This patient had a perforated gastric ulcer.
Chilaiditi syndrome.
Close-up of the right hemidiaphragm on a conventional chest radiograph (A)and an axial CT scan at the level of the diaphragm (B),both demonstrating air beneath the diaphragm that could be confused for free air (open black arrowsin [A]and [B]). Careful evaluation of this air demonstrates several haustral folds (solid black arrowsin [A]and solid white arrows in [B]), which indicate this is a loop of colon interposed between the liver and the diaphragm (Chilaiditi syndrome) rather than free air.
Falciform ligament sign.
A,Free intraperitoneal air may surround the normally invisible falciform ligament on the anterior edge of the liver causing that thin, soft tissue structure to become visible (solid white arrows)just to the right of the upper lumbar spine. Notice also that both sides of the stomach wall are visible (Rigler sign) (dotted white arrow),and there is increased lucency to the right upper quadrant (solid black arrow)in this patient with a large pneumoperitoneum from a perforated gastric ulcer. B,The falciform ligament (white arrow)is outlined by free air (FA) on either side of it, anterior
Extraperitoneal air seen on CT.
Air is seen in the retroperitoneum (solid black arrow)on this axial CT scan of the upper abdomen. Air outlines the inferior vena cava (solid white arrow)and the aorta (dotted white arrow). Unlike free air, extraperitoneal air is streaky, relatively fixed in position and outlines extraperitoneal structures like the vena cava, aorta, psoas muscles, and kidneys.
Pneumatosis seen in profile.
Close-up of the right lower quadrant in an infant demonstrates a thin curvilinear lucency that parallels the lumen of the adjacent bowel (white arrows), an appearance characteristic of gas in the bowel wall seen in profile. In infants the most common cause for this finding is necrotizing enterocolitis, a disease found mostly in premature infants in which the terminal ileum is most affected. Pneumatosis intestinalis is pathog- nomonic for necrotizing enterocolitis in infants.
Pneumatosis seen en face.
Close-up of the right lower quadrant in another infant shows multiple faint, mottled lucencies in the right lower quadrant, which is the appearance of pneumatosis intestinales when seen en face. The density has the same appearance as air mixed with stool, but can be distinguished from stool because it occurs in areas stool might not be expected, and it does not change over time. This infant also had necrotizing enterocolitis.
Pneumatosis cystoides intestinalis.
Axial CT scan of the upper abdomen win- dowed for lung technique shows a cluster of air-containing cysts (solid white arrows)associated with the left colon, characteristic of pneumatosis cystoides intestinales,a rare but benign condition in which air-containing cysts form in the submucosa or serosa of the bowel.
Necrosis of bowel from mesenteric ischemia
Axial computed tomography image of the pelvis demonstrates multiple loops of bowel with punctate collections of air throughout their walls consistent with pneumatosis (white arrows). The patient had widespread ischemia of the bowel from mesenteric vascular disease. Pneumatosis that results from bowel necrosis is an ominous sign.
Portal venous gas.
A,Numerous small black branching structures are visible over the periphery of the liver (white circle). This is air in the portal venous system, a finding most often associated with necrotizing enterocolitis in infants, but which can also be seen in adults, usually with bowel necrosis. Unlike air in the biliary system, this air is peripheral rather than central and has numerous branching structures instead of the few tubular structures seen with pneumobilia. B,Close-up of axial CT scan through the liver shows air in the portal venous system (white arrows)in a patient with mesenteric vascular disease.
Air in the biliary tree.
Frontal view of the upper abdomen from an upper gastro- intestinal series demonstrates several air-containing tubular structures over the central portion of the liver consistent with air in the biliary system (white circle). There is also barium in the gallbladder (white arrow). This patient had a history of a prior sphincterotomy for gallstones so that reflux of air and barium into the biliary system would be expected.
Gallstone ileus.
The three key findings of gallstone ileus are present on this study. A,Axial CT scan of the upper abdomen shows air in the lumen of the gallbladder (black arrow)and dilated small bowel (white arrow)consistent with a mechanical small bowel obstruction. B,At a lower level, another axial CT scan of the abdomen shows a large calcified gallstone inside the small bowel (dotted white arrow)and additional proximal, dilated loops of small bowel (solid white arrow). The gallstone had eroded through the wall of the gallbladder into the duodenum and then began a journey down the small bowel before becoming impacted and producing obstruction.
