Abdomen Patterns

Chapter 32

Abdomen Patterns

Beverly L. Harger

Lisa E. Hoffman

Richard Arkless

AB1. Abdominal Calcifications

AB2. Pneumoperitoneum

AB3. Abnormal Localized Intraperitoneal Gas Collections

AB4. Pneumoretroperitoneum

AB5. Abnormal Bowel Gas Resulting from Obstruction

AB6. Ascites

AB7. Enlarged Organ Shadows

AB8. Abdominal Masses

AB9. Diseases of the Gallbladder

AB10. Vascular Calcifications

AB11. Miscellaneous Radiopacities and Abdomen Artifacts

 

AB1 Abdominal Calcifications

Numerous pathologic processes in the abdomen may cause soft-tissue calcification. A pattern approach that evaluates the morphologic features, location, and mobility of an abnormal opacity often provides sufficient information for a definitive diagnosis or at least narrows the etiologic considerations to a few possibilities.3 Almost all abdominal calcifications fall into four major morphologic categories. Each one of the four categories possesses characteristic roentgen features based on shape, border sharpness, marginal continuity, and internal architecture.3 The four morphologic categories are concretions, conduit wall calcification, cystic calcification, and solid mass calcification (Table 32-1).3 A concretion represents calcification within the lumen of a vessel or hollow viscera. The most common of these are listed in Table 32-2. Concretions typically do not pass through vascular or visceral walls; therefore, they are seldom seen outside their expected locations. Calcification within the wall of fluid-containing hollow tubes (e.g., parts of the urinary tract, the pancreatic ducts, vas deferens, biliary ductal system, and arteries and veins) is known as a conduit wall pattern. Calcification within the wall of a hollow or fluid-filled mass is characteristic of the cystic morphologic category. Last, the solid mass calcification can be found anywhere within the abdomen and may be central or peripheral, adjacent to or within organs, or in the intraperitoneal or retroperitoneal spaces.

TABLE 32-1

COMPARISON OF ROENTGEN FEATURES OF ABDOMINAL CALCIFICATIONS

Morphology Shape Border Margin Internal appearance
Concretion (stone) Varied (round or oval, faceted); occasional unique shape such as star-shaped bladder calculi or “staghorn” calculus Sharp, clearly defined; may occasionally have irregular bulges Continuous; if outer perimeter is incomplete, it is unlikely a stone Varied
Multiple laminations (unequivocal indication of concretion)
Homogenously dense
Single central lucency
Outer margin is dense and continuous with lucent internal appearance
Conduit Tubular, track-like appearance when viewed in profile; ring-like appearance when viewed en face May be indistinct Discontinuous, irregular None; presence of internal radiopacity suggests another morphologic category
Cystic Round or oval; may be compressed on one side; shape depends on location Smooth, curvilinear rim of opacification Rim calcification may be continuous or interrupted; short arcs may be only visibly calcified portion Surfaces with extensive calcium deposition that are not tangential to x-ray beam may simulate internal matrix (mass-like) calcification; interior calcifications less dense than marginal calcifications
Mass Varied Irregular calcified border; occasionally, the border is more densely calcified than interior resembling cyst Interrupted; margins typically appear notched or slightly angulated Extensive interior calcification; mottled densities with scattered radiolucencies; flocculent calcification superimposed on lucent background

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From Baker SR: The abdominal plain film, ed 1, Norwalk, CT, 1990, Appleton & Lange.

TABLE 32-2

SITES OF CONCRETIONS

Site Comments
Pelvic veins (phleboliths) Represent calcification within preexisting venous thrombi; typical appearance is round opacity with a central or slightly eccentric single lucency
Gallbladder (choleliths) Circumferential laminations are encountered frequently
Urinary tract (nephroliths) Ureteral calculi are often angular; bladder stones are most often smooth and laminated; renal calculus occupying the pelvicaliceal system may have an appearance of a “staghorn” distinguishing it from other abdominal radiopacities
Prostate (prostatolith) Predominantly within elderly men
Appendix (appendicolith, fecalith) Usually encountered in younger patients; appendicoliths often are laminated; essentially considered a surgical indicator
Pancreas Typically present as discrete opacities that cross the midline at the level of the L1–L2 vertebral bodies; discrete opacities present in head of pancreas alone (25% of cases)

Several limitations of classification according to radiographic morphology exist. When a calcification is small, it is difficult to categorize. Furthermore, faint calcification cannot be classified if no information about margins or internal matrix can be ascertained.3

The following is a brief presentation of each of the four major morphologic categories (AB1a through AB1d) with the most common etiologic considerations.

AB1a Concretions

A concretion (also called a stone or calculus, using the suffix “lith”) is a calcified mass that forms in a tubular or hollow structure such as the lumen of a vessel or hollow viscus. A fairly constant appearance of concretions is a sharp, clearly defined external margin that almost always is continuous.3 This continuity may help differentiate a concretion in a hollow viscus (e.g., renal pelvis, gallbladder, urinary bladder) from a calcified cyst. Discontinuity of the outer margin makes a diagnosis of a stone unlikely. The internal architecture of concretions may vary in appearance. Concretions may have concentric laminations, contain a slightly eccentric area of lucency, or be homogenously dense. On occasion, a concretion’s outer margin is dense and continuous with a lucent internal appearance. Generally, concretions are seen in association with anatomic structures and do not pass through the vascular or visceral wall. Concretions appearing outside of common, expected anatomic locations are unusual.

Concretion Comments
Appendicolith (Fig. 32-1) Frequently associated with current or future appendiceal perforation, especially in children;19 it is seen most commonly in the right lower quadrant but location may vary
Cholelithiasis (Fig. 32-2) (p. 1308) 10% to 15% are calcified and therefore visible on plain film;31,63 cholelithiasis occurs more frequently in elderly and obese people, predominantly in women;31 typically, cholelithiasis occurs in the right upper quadrant, but the location may vary
Pancreatic calculi (Fig. 32-3) Most commonly associated with chronic pancreatitis secondary to alcoholism;62 the typical appearance is multiple, tiny, dense, discrete opacities that cross the midline at the level of L1–L2
Phleboliths (Fig. 32-4) Most commonly encountered calcification in pelvis;3 they are frequently multiple and bilateral; sometimes a concentric or slightly eccentric interior lucency occurs; they can be confused with urinary tract stones; should not appear midline; collections of phleboliths outside the area of the pelvic bowl veins may indicate the presence of a soft-tissue hemangioma
Prostatic calculi (Fig. 32-5) Multiple concretions of varied sizes clustered behind pubic symphysis in men usually older than 40 years of age;3 this condition results from prior prostatitis; prostatic calculi often are asymptomatic
Urinary tract calculi (Figs. 32-6 to 32-8) May be seen in the renal calyces or pelvis, ureters, and bladder; they are uncommon in the urethra;53 sometimes urinary tract calculi are associated with conditions producing hypercalcemia or hypercalciuria3

 

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FIG 32-1 Appendicoliths. A, Concretion in the right lower quadrant in a child. Appendicolith may indicate appendicitis with perforation and abscess. Notice the sharp, continuous external margin characteristic of a concretion. The concretion in this case is uniformly dense. B and C, Large concretion of the right lower abdominal quadrant consistent with appendicolith (arrows) in a second patient. D, Uniform radiodense shadows representing foreign bodies within the appendix. B and C, Courtesy C. Robert Tatum, Davenport, IA.
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FIG 32-2 Cholelith. A and B, Laminated gallstone with continuous outer margin typical of a concretion (arrow) in different patients. A, Courtesy John A.M. Taylor, Seneca Falls, NY.
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FIG 32-3 A and B, Two patients with pancreatic calculi and chronic pancreatitis in a patient with alcoholism. This is the typical appearance of numerous dense, discrete opacities that cross the midline at the level of L1 to L2 (arrow). The normal pancreas is not visible on abdominal plain films.
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FIG 32-4 A and B, Numerous phleboliths in two patients. Phleboliths frequently are multiple and bilateral, and they are asymptomatic. They are inconsequential concretions of thrombi attached to the walls of veins. Observe the concentric interior lucency of the phleboliths (arrows). These should not be confused with ureteral stones or calcifications of a pelvic mass.
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FIG 32-5 The numerous tiny calculi projecting above the pubic symphysis seen in this patient (arrows) are typical of the intraductal calculi often occurring in patients who have chronic inflammation of the prostate.
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FIG 32-8 Staghorn calculi. A, Anteroposterior projection shows a concretion taking the shape of the pelvicaliceal system (staghorn calculus). B, Lateral view. Superimposition of the concretion over the vertebral body indicates the retroperitoneal location. C, Second patient with staghorn calculus. A and B, Courtesy Cynthia Peterson, Toronto, Ontario, Canada.
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FIG 32-7 Ureteral stones. Intravenous urogram demonstrates multiple small opacities located within the lower segment of the ureter (arrows).
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FIG 32-6 Bladder calculi. Three homogeneously dense bladder stones with a continuous rim of calcification typical of concretions. Incidentally noted is a phlebolith with the diagnostic concentric lucency that should not be mistaken for a ureteral stone (arrow).

AB1b Conduit Wall Calcification

Conduits are channels or tubular structures through which fluids are conducted.3 Conduit wall calcifications are confined to only the tubular walls, which are seen radiographically as parallel, linear opacities or, when seen on end, as ring-like calcifications.3 Therefore, any internal radiopacity indicates another class of calcification.

The calcification in conduit walls is not homogeneous. The most common site is in the walls of arteries, where one sees interrupted but basically linear calcifications.3 This feature helps differentiate them from concretions, which usually have a continuous calcified external margin. The calcification also can outline a vessel’s branching pattern.3

Location Comments
Aorta and iliac arteries (Fig. 32-9) Occurs mostly as a result of atherosclerosis; patients younger than 40 years of age are rarely affected; this may be associated with smoking or diabetes; patients can have hypertension or coronary artery disease
Renal arteries Arise from abdominal aorta at or near L1 and usually extend laterally or infralaterally; calcification occurs primarily as a consequence of atherosclerosis or diabetes;2,60 this often is accompanied by aortic calcification
Splenic artery (Fig. 32-10) Frequently calcifies and has a characteristic serpentine course in the left upper quadrant
Iliac veins and inferior vena cava Veins not subjected to either high pressure or pulsatile flow and are relatively protected from the risk of intimal layer damage (see Figs. 32-4 and 32-68).3
Gallbladder wall (Fig. 32-11) Also known as porcelain gallbladder, can resemble a large gallstone; a significant percentage of these patients also develop gallbladder cancer, usually adenocarcinoma;* typically, prophylactic surgery is indicated
Vas deferens (Fig. 32-12) Most often in patients with diabetes; rarely secondary to infection;12,24,36 most often bilateral, curved, symmetric, and parallel to the pubic rami

*References 5, 11, 18, 34, 45, and 52

 

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FIG 32-9 Abdominal aorta and iliac arteries calcification. A, Anteroposterior projection. Tubular appearance characteristic of conduit wall calcification. The aortic bifurcation is seen clearly (arrow). B, Lateral view. Notice that the anterior and posterior walls are parallel and the abdominal aorta diameter does not exceed 3.5 cm. Aneurysm should be suspected if the diameter of the abdominal aorta exceeds 3.5 cm. A spondylolytic spondylolisthesis of L5 also is visible (arrow). Courtesy John A.M. Taylor, Seneca Falls, NY.
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FIG 32-10 Splenic artery calcification. A and B, Convoluted tubular appearance is typical of the splenic artery (arrows) in the right upper abdominal quadrant seen here in the anteroposterior and lateral view. C, A second case of similar appearance (arrows).
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FIG 32-11 Calcification within the wall of the gallbladder. A, Anteroposterior projection. Calcification within the wall of the gallbladder mimics a cyst. This condition is important to recognize because adenocarcinoma is a common complication. B, Lateral view confirms the intraperitoneal location (arrow). Conduit calcification of the abdominal aorta also is visible (arrowhead). Courtesy John A.M. Taylor, Seneca Falls, NY.
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FIG 32-12 Vas deferens calcification. A and B, Two cases of tram-like calcification paralleling the superior pubic rami are typical of vas deferens calcification. The location helps differentiate this from arterial calcification.

AB1c Cystic Calcification

Calcium deposition in the wall of an abnormal fluid-filled structure defines cystic calcification.3 Calcium around the surface of a tumor occasionally mimics this appearance. Examples of cystic calcification include epithelial-lined cysts, pseudocysts that have fibrous integument, and arterial aneurysms. Calcification shows up as a smooth, curvilinear rim of opacity.3 This rim-like appearance usually is larger than that of conduit wall calcification; however, calcification may be interrupted in spots in both types, appearing as an incomplete circle. Single, incomplete calcified margins likely represent a cystic density in contrast to a concretion, in which one should expect a continuous margin of calcification.3 The external border of the cyst usually is smooth, but the internal aspect is irregular, reflecting the interface with the contained fluid.3 In contrast to a solid mass type of pattern, the outer margin of a cystic structure usually exhibits a relatively well-defined margin. Adjacent organs or vessels may be displaced or distorted by either solid masses or cystic structures.

Cyst Comments
Left Upper Quadrant (Above L3)
Spleen (Fig. 32-13) Two thirds of splenic cysts caused by Echinococcus granulosis (rare in the United States);61 other possibilities include hemorrhagic and serous cysts, usually secondary to trauma;14 cystic changes may be secondary to subcapsular hematoma and metastatic mucinous adenocarcinoma of the ovary;48 occasionally an aneurysm of splenic artery may mimic a cyst; see also the Renal and Adrenal sections that follow
Right Upper Quadrant (Above L3)
Liver Rare hepatic cysts except those associated with E. granulosis; occasionally, gallbladder carcinoma calcification can reside high and inside the liver7,22,41
Right Or Left Upper Quadrant
Renal (Fig. 32-14) Benign and malignant neoplasms of the kidney and renal cysts; renal cysts are more common with advancing age, but usually they do not calcify;32,35,51 renal artery aneurysm and subcapsular hematoma also may present as cystic calcifications
Adrenal (Fig. 32-15) Infrequent; pseudocysts are the most common cysts to calcify;47 calcified cystic pheochromocytomas and other benign and malignant tumors are rare21,55,69
Midabdomen
Pancreas Rare calcification of the wall of a pancreatic pseudocyst;37 cystic calcifications may be seen in benign and malignant tumors20
Right Lower Quadrant (Below L3)
Appendix Mucocele calcification rarely appears as a calcified cyst; it occurs primarily in middle-aged persons and is slightly more common in men15
Left Lower Quadrant (Below L3) Least likely of the abdominal regions to contain calcific densities; when present, they are likely to be ureteral stones, vascular densities, and leiomyomas; cystic calcifications are especially rare
Pelvic bowl
Bladder Schistosomiasis of the bladder, worldwide, is the most common cause of mural calcification and is seen as a thin, continuous curvilinear calcification of cyst type; it is rare in the United States.66
Ovary Most common ovarian lesion: cystic teratoma (dermoid cyst);68 about 10% of cystic teratomas show calcification of cyst type;13,68 benign cystadenomas and cystadenocarcinomas may appear as curvilinear calcifications of cystic type;46 any cystic calcification in this area must be considered a possible malignancy unless proved otherwise
Any Location
Mesentery and omentum Mesenteric and omental cysts are rare; 60% occur before 5 years, most often found in small bowel mesentery9
Cystic Calcifications That Cross the Midline
Aorta Abdominal aortic aneurysm: most common abnormality with the radiographic appearance of the cystic calcification in this location.3

 

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FIG 32-13 Calcified splenic cyst. A, Observe the smooth, curvilinear rim of opacity in the wall of the cyst; although continuous in this case, most cysts have an interrupted rim of calcification. A central, horizontal line of calcification indicates septation (arrow). B, Another patient demonstrates a smaller splenic cyst (arrows). B, Courtesy Gary Longmuir, Phoenix, AZ.
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FIG 32-14 Renal artery aneurysm. Calcified cyst overlying the right transverse process of the L3 segment in the frontal projection (A) and L3 intervertebral disc space in the lateral view (B). C, Axial computed tomography details the cyst as an aneurysm of the renal artery (arrows). Courtesy Michael Buehler, Carol Stream, IL.
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FIG 32-15 Massive adrenal cyst with septations. This massive lesion proved to be adrenal carcinoma (arrows). Contrast opacification of the pelvicaliceal system and proximal ureter is noted (crossed arrows).

AB1d Solid Mass Calcification

This category comprises the most diverse presentation of the four. Irregularly calcified borders and complex internal architecture are characteristic of solid mass calcification.3 Prominent but irregular and inhomogeneous calcification in the more central portion of the mass and discontinuity of the outer border are encountered frequently.3

Mass Comments
Left Upper Quadrant
Spleen (Fig. 32-16) Splenic densities most often resulting from calcium deposition in granulomas, often from histoplasmosis if multiple or occasionally from tuberculosis.23,59 Frequently they have the morphologic appearance of concretions.
Right Upper Quadrant
Liver Most common universal cause of solid calcifications: tuberculosis and histoplasmosis;1,17 calcified metastases (usually from colon and ovary) and benign neoplasms, such as cavernous hemangioma, may cause solid calcifications.1
Right or Left Upper Quadrant
Adrenal (Fig. 32-17) In adults, a normal-sized adrenal gland with calcification may be seen secondary to tuberculosis, Addison disease, and old neonatal hemorrhage; solid adrenal calcification in an enlarged gland may result from cortical carcinoma; adenomas rarely calcify6
Renal (Fig. 32-18) Hypernephromas (renal cell carcinoma) make up 90% of all solid mass type of calcification involving the kidneys;16 among inflammatory diseases, tuberculosis most frequently shows calcification;65 solid mass calcification can occur in other primary malignancies, metastases (rare), and hamartomas54
Midabdomen
Pancreas (Fig. 32-19) Pancreatic cystadenoma and cystadenocarcinoma solid mass calcification varying from a large stellate to closely aggregated solid masses to scattered clumps29,49
Pelvic Bowl
Bladder Detectable calcifications seen in only 0.5% of bladder tumors;44 bladder calcification is rare with urinary tuberculosis;28 schistosomiasis can calcify but is rare in the United States
Uterine (Fig. 32-20) Coarse, granular calcifications resembling popcorn or cauliflower developing within necrotic areas of uterine leiomyoma (common) and leiomyosarcoma (rare).57
Ovary Two thirds of all ovarian malignancies: papillary serous cystadenocarcinomas that may calcify at the primary site and in metastatic deposits;8,64 the calcification, known as psammomatous calcification, can vary from a flocculent, sharply demarcated focus to a less well-defined density and sometimes are found throughout the abdomen
Any Location
Intestinal tract Adenocarcinomas or colloid carcinomas of the intestinal tract with characteristically mottled, speckled, or granular pattern calcification; however, calcified small bowel tumors rarely are seen on radiographs; when seen, carcinoid tumors are more common33
Subcutaneous (Fig. 32-21) Extensive calcification resulting from scleroderma, dermatomyositis, and subcutaneous fat necrosis; this calcification can project over the abdomen and seem to be intraabdominal27
Lymph node (Fig. 32-22; see also Fig. 32-27, A) Mesenteric lymph nodes: most common abdominal nodes to calcify;58 they are one of the more common types of abdominal calcifications seen; healed tuberculosis is sometimes the cause of these calcifications, with exposure usually occurring several decades previously58
Peritoneal Psammomatous calcifications appearing within ovarian cystadenocarcinoma and its peritoneal implants; they may be widespread64
Scars (Fig. 32-23) Occasionally peculiar-shaped calcifications, often located in the abdominal wall

 

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FIG 32-16 Splenic mass calcifications in two different patients. A, Splenic granulomas are seen as solid mass calcification in the left upper quadrant (arrows). B, Multiple calcified granulomas. These are most often from histoplasmosis.
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FIG 32-17 A and B, Bilateral adrenal gland calcification in two cases. The size and location of the adrenal glands are visible because of calcification (arrows). These normal-sized adrenal glands show calcification most likely secondary to tuberculosis, Addison disease, or old neonatal hemorrhage.
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FIG 32-18 Solid mass calcification. This was proved to be renal mass calcification from tuberculosis. Solid calcifications share the common feature of a nongeometric inner architecture and irregular, often incomplete margins.
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FIG 32-19 Solid mass calcification of the pancreas. A, Anteroposterior projection. Notice that the calcifications are close to the midline on the right and extend far to the periphery to the left. B, Right anterior oblique view. These scattered clumps of calcification of the pancreas may indicate benign or malignant lesions. Pancreatic lithiasis associated with pancreatitis typically present as small, discrete opacities (concretions).
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FIG 32-20

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Feb 16, 2016 | Posted by in RESPIRATORY IMAGING | Comments Off on Abdomen Patterns
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