The Spread and Localization of Intraperitoneal Abscesses

I have documented that the spread of infection within the peritoneal cavity is governed by (a) the site, nature and rapidity of outflow of the escaping visceral contents; (b) mesenteric partitions and peritoneal recesses; (c) gravity; (1) intraperitoneal pressure gradients; and (2) the position of the body.6,14,18,36

The dynamic pathways of flow of intraperitoneal fluid in vivo have been established in a series of adult patients by peritoneography.6,14 The peritoneal reflections and recesses provide watersheds and drainage basins for the spread and localization of infection (Table 3-1).

Intraabdominal abscesses may be radiologically manifested by demonstrating (a) a soft-tissue mass, (b) a collection or pattern of extraluminal gas, (c) viscus displacement, (d) loss of normally visualized structures, (e) fixation of a normally mobile organ, or (f) opacification of a communicating sinus or fistulous tract. Secondary signs include scoliosis, elevation or splinting of a diaphragm, localized or generalized ileus, and pulmonary basilar changes. These pathways and localizing features are evident not only by conventional radiologic tech niques, but they have also been confirmed by ultraso-

37 38 39

nography, isotopic studies and computed tomog-raphy.40,41 Knowledge of the preferential pathways of spread and subsequent compartmentalization permits the early diagnosis of abscess formation often remote from its site of origin.6,36

Pelvic Abscesses

Fluid introduced into the inframesocolic compartment almost immediately seeks the pelvic cavity, first filling out the central pouch ofDouglas (cul-de-sac)42 and then

Table 3-1. Radiologic-Anatomic Classification of

Intraperitoneal Abscesses'

Su pram.es o co lie Inframesocolic

Right subphrenic Pelvic

Anterior Paracolic

Posterior Right

Right subhepatic Left

Anterior Infracolic

Posterior (Morison's pouch) Right

Left subphrenic Left Lesser sac aModified from Meyers MA, Whakn JP.3('

Intraperitoneal Hematoma

Fig. 3-42. Distinction between fluid collections in the lesser sac and gastrohepatic recess in a patient with metastatic ovarian carcinoma.

(a) CT demonstrates two fluid collections compressing the midbody of the stomach (S). One within the gastrohepatic recess (GHR) is seen anteriorly, while a lesser sac collection (LS), confined laterally by the gastrosplenic ligament, is seen posteriorly.

(b) T1-weighted and (c) T2-weighted MR images show that the lesser sac collection exhibits high signal intensity on both, compatible with a resolving hematoma in the extracellular methemoglobin phase. A thin hypointense rim around the collection is attributed to hemosiderin within macrophages. The gastrohepatic collection is nonhemorrhagic ascites, with signal similar to cerebrospinal fluid.

Fig. 3-42. Distinction between fluid collections in the lesser sac and gastrohepatic recess in a patient with metastatic ovarian carcinoma.

(a) CT demonstrates two fluid collections compressing the midbody of the stomach (S). One within the gastrohepatic recess (GHR) is seen anteriorly, while a lesser sac collection (LS), confined laterally by the gastrosplenic ligament, is seen posteriorly.

(b) T1-weighted and (c) T2-weighted MR images show that the lesser sac collection exhibits high signal intensity on both, compatible with a resolving hematoma in the extracellular methemoglobin phase. A thin hypointense rim around the collection is attributed to hemosiderin within macrophages. The gastrohepatic collection is nonhemorrhagic ascites, with signal similar to cerebrospinal fluid.

Intraperitoneal Hematoma

the lateral paravesical fossae (Figs. 3-44 and 3-45). A small amount in the left infracolic space readily pursues this course, but on the right, it is first arrested at the confluence ofthe small bowel mesentery with the colon before it overflows into the dependent recesses of the pelvis. This pathway is a function primarily of gravity and explains why the pelvis is the most common site of

Early Ascites

Fig. 3—43. MRI anatomy of the lesser sac. Fluid in the lesser sac.

(a-c) In a case of ascites, T1-weighted coronal images demonstrate fluid in the lesser sac (LS) demarcated by the gastrohepatic ligament (GHL), gastrocolic ligament (GCL), the gastrosplenic (GSL) and splenoreal (SRL) ligaments, and the transverse mesocolon (TMC). The lesser sac communicates with Morison's pouch (MP) through the epiploic foramen of Winslow deep to the hepatoduodenal ligament (HDL), through which the proper hepatic artery (PHA) can be seen to course. Further subhepatic fluid in the left posterior perihepatic space (LPHS) is separated from the lesser sac by the gastrohepatic ligament. Greater peritoneal fluid is also seen in the left infracolic space (LICS) in relation to the small bowel mesentery (SM) and sigmoid mesocolon (SMC). S = stomach; D = duodenum; C = colon; DCL = duodenocolic ligament; P = pancreas; SA = splenic artery, SV = splenic vein; PCL = phrenicocolic ligament. (Reproduced from Chou C-K et al.35)

any residual abscess formation following generalized peritonitis (Figs. 3-46 and 3-47).

Fluid within the pouch of Douglas may be identified easily on supine plain film as a soft-tissue density superior to the urinary bladder (Fig. 3-48), at times with symmetric circular extensions representing further fluid collections within the paravesical fossae.44 In cases of

Peritoneal Recesses

Fig. 3—44. Fluid accumulation in pelvic recesses.

(a) A small amount of contrast medium introduced into the peritoneal cavity immediately gravitates to the pelvis, filling out the central pouch of Douglas (PD) and then the lateral paravesical fossae (PV).

(b) In another patient, erect view shows a larger amount of intraperitoneal contrast medium distending the midline pouch of Douglas (PD) and the lateral paravesical fossae (PV). The urinary bladder (B) is opacified.

Fig. 3—44. Fluid accumulation in pelvic recesses.

(a) A small amount of contrast medium introduced into the peritoneal cavity immediately gravitates to the pelvis, filling out the central pouch of Douglas (PD) and then the lateral paravesical fossae (PV).

(b) In another patient, erect view shows a larger amount of intraperitoneal contrast medium distending the midline pouch of Douglas (PD) and the lateral paravesical fossae (PV). The urinary bladder (B) is opacified.

Fig. 3-45. Intraperitoneal fluid in the pelvic recesses.

CT shows massive ascites accumulating in the pelvic spaces. Fluid is present in the pouch of Douglas (DP), between the rectum (R) posteriorly and the uterus (U) and broad ligaments (arrows) anteriorly.

Fluid The Pouch Douglas

abdominal trauma, it may be the earliest and most reliable sign of the laceration or rupture of an organ. If doubt exists, a prone film permits the fluid to escape and the radiographic density is lost. Mass displacements by an abscess are seen most easily by extrinsic distortion of the dome of the urinary bladder, by compression on the rectosigmoid junction, or by displacement of the sigmoid colon, usually posteriorly and superiorly (Figs. 349 through 3-51). Lateral displacement of sigmoid loops may occur if the abscess extends beyond the midline. A huge abscess may arise out of the pelvis, displacing the intestine superiorly and to the side.

Fluid collections in additional pelvic fossae may be identifiable by CT and ultrasonography.45

Right Subhepatic and Subphrenic

Abscesses

From the pelvis, fluid ascends both paracolic gutters. Passage up the shallower left one is slow and weak, and cephalad extension is limited by the phrenicocolic lig-ament.6,38 The major flow from the pelvis is up the right paracolic gutter6 (Fig. 3-52). It then progresses deep to the inferior edge of the liver into the right subhepatic space, particularly draining into its posterior extension (Morison's pouch) (Figs. 3-53 through 3-55). The right paracolic gutter consistently provides an avenue of spread for exudates. Abscess formation may coalesce in the anterior subhepatic space (Fig. 3-56), but this is unusual. Fluid preferentially seeks first the most dependent recess of Morison's pouch. This is formed by the triangular groove between the lateral aspect of the descending duodenum and the underlying right kidney, just above the beginning of the transverse mesocolon (Fig. 3-57). Thereafter, fluid occupies the entire pouch (Figs. 3-57 through 3-59). This drainage pathway from the pelvis is so constant that if the right paracolic groove can be referred to as a "gutter," then the "sewer" into

Pouch Douglas

Fig. 3-46. Pouch of Douglas abscess.

CT demonstrates an abscess with an enhancing wall (A), secondary to appendicitis, that has localized in the cul-de-sac between the rectum (R) and the uterus (U). B = urinary bladder.

Fig. 3-46. Pouch of Douglas abscess.

CT demonstrates an abscess with an enhancing wall (A), secondary to appendicitis, that has localized in the cul-de-sac between the rectum (R) and the uterus (U). B = urinary bladder.

Echo Abdo Pelv

Fig. 3—47. Pouch of Douglas abscess.

(a) T2-weighted fat-suppressed spin-echo MR image reveals a complex fluid collection (arrowheads) behind the urinary bladder (b). Low-signal intensity debris is layered in the dependent portion of the abscess.

(b) Sagittal gadolinium-enhanced Tl-weighted fat-suppressed SGE MR image shows substantial enhancement of the wall of the abscess (arrows).

(Reproduced from Semelka et al.43)

Fig. 3—47. Pouch of Douglas abscess.

(a) T2-weighted fat-suppressed spin-echo MR image reveals a complex fluid collection (arrowheads) behind the urinary bladder (b). Low-signal intensity debris is layered in the dependent portion of the abscess.

(b) Sagittal gadolinium-enhanced Tl-weighted fat-suppressed SGE MR image shows substantial enhancement of the wall of the abscess (arrows).

(Reproduced from Semelka et al.43)

which it preferentially drains its contaminated material is clearly Morison's pouch.

Intraperitoneal fluid lateral to the liver may be radio-graphically noted by identifying the lateral margin of the liver that becomes medially displaced (Hellmer's sign47) (Figs. 3-60 and 3-61). The appreciable difference in density is secondary to the attenuation coefficients between ascitic fluid and the hepatic parenchyma.44'48 Blood, however, does not possess any difference in attenuation from the liver to be seen in this manner.

Intraperitoneal Blood

Fig. 3—48. Intraperitoneal blood gravitating to the pelvic recesses.

(a) This can be identified as a soft-tissue density (arrows) superior to the urinary bladder in this intravenous urogram.

(b) In another patient with a large amount of blood in the pelvis, CT correlation can be made. Note the hematocrit effect (arrows) with the high attenuation acute hemorrhage becoming dependent in the pararectal fossae.

It is important to recognize that only after Morison's pouch is contaminated does the infected material reach the right subphrenic space (Figs. 3-62 through 3-67).

The fluid extends around the inferior edge of the liver or laterally from Morison's pouch along the inferior reflection of the right coronary ligament and then text continues on page 89

Mammogram Tissue Spread

Fig. 3—49. Pelvic abscess in a child postappendectomy.

A large soft-tissue mass compresses and separates the rectosigmoid junction and the urinary bladder (B). A redundant sigmoid loop seen in this lateral view projects in this area but is truly off the midline.

Fig. 3—49. Pelvic abscess in a child postappendectomy.

A large soft-tissue mass compresses and separates the rectosigmoid junction and the urinary bladder (B). A redundant sigmoid loop seen in this lateral view projects in this area but is truly off the midline.

Abscess Pelvic

Fig. 3—50. Pelvic abscess secondary to sigmoid diverticulitis.

Following perforation of a diverticulum of the sigmoid colon (arrow) in the left lower quadrant, drainage into the pelvis results in an abscess (A) in the pouch of Douglas, shown by its characteristic compression on the rectosigmoid junction.

Rectosigmoid Junction

Fig. 3-51. Large pelvic abscess drains from an appendiceal abscess that also deforms the caput of the cecum. Gravitational flow is clearly indicated in the frontal (a) and lateral (b) views, with the large pelvic abscess displacing the rectum posteriorly against the sacral hollow. (Reproduced from Meyers.6)

Fig. 3-51. Large pelvic abscess drains from an appendiceal abscess that also deforms the caput of the cecum. Gravitational flow is clearly indicated in the frontal (a) and lateral (b) views, with the large pelvic abscess displacing the rectum posteriorly against the sacral hollow. (Reproduced from Meyers.6)

Pelvic Gutters

Fig. 3-52. Abscess in the right paracolic gutter.

Unenhanced CT shows a gas-containing abscess (arrow) encapsulated within the right paracolic gutter.

Right Paracolic Gutter

Fig. 3-53. Preferential spread up right paracolic gutter.

Peritoneography in a patient demonstrates that contrast material, after first filling the pelvis (Pv), then extends directly up the right paracolic gutter (PG). It then outlines the hepatic angle (H) and progresses preferentially into Morison's pouch (MP). (Reproduced from Meyers.6)

Fig. 3-54. Contrast medium injected through a misplaced cystotomy tube (T) whose tip is outside the urinary bladder. The fluid proceeds up the right paracolic gutter (PG) to the subhepatic spaces (SH).

Pelvic Gutters

Fig. 3-55. Leak from anastomotic site following an ileotransverse colostomy. Lateral radiograph shows that extravasation seeks the right subhepatic space (arrows).

Fig. 3-55. Leak from anastomotic site following an ileotransverse colostomy. Lateral radiograph shows that extravasation seeks the right subhepatic space (arrows).

Fig. 3—56. Right paracolic and anterior subhepatic abscesses, postappendectomy.

Exudate containing a few gas bubbles (arrows) extends up the right paracolic gutter to a subhepatic abscess. This depresses the proximal transverse colon (C) and, by lifting the edge of the liver from its bed of extraperitoneal fat, results in loss of visualization of the hepatic angle. (Reproduced from Meyers.6)

Doge Cap Sign Morison Pouch

Fig. 3—57. The triangular dependent recess of Morison's pouch is opacified by a small amount of contrast medium. This is bounded posteriorly by the kidney (K), medially by the descending duodenum (D), and inferiorly by the proximal transverse colon (C). The outline particularly of gaseous collections at this site has been referred to as the Doge's cap sign, since its configuration typically has the shape of a peaked cap reminiscent of "Il corno," the renaissance headgear worn by the Doge of Venice.46 (Reproduced from Meyers. )

Morison PouchMorison Pouch

Fig. 3-58. Abscess of Morison's pouch.

Injection into the localized abscess cavity through a drainage tube identifies its size and position. Note the relationship of the abscess to the 10th and 11th posterior ribs. Residual barium outlines the hepatic flexure of the colon, which serves as the inferior boundary of the abscess. The development of pyogenic membranes may prevent spread to other compartments. (Reproduced from Meyers.6)

Fig. 3-58. Abscess of Morison's pouch.

Injection into the localized abscess cavity through a drainage tube identifies its size and position. Note the relationship of the abscess to the 10th and 11th posterior ribs. Residual barium outlines the hepatic flexure of the colon, which serves as the inferior boundary of the abscess. The development of pyogenic membranes may prevent spread to other compartments. (Reproduced from Meyers.6)

Fig. 3-59. Abscess of Morison's pouch.

Erect view identifies a conspicuous air-fluid level (arrow) characteristically in relation to the upper pole of the right kidney at the level of the 11th rib.

Fig. 3-60. Fluid lateral to the liver.

(a) Plain film visualization of the lateral margin of the right lobe (arrows) is highlighted by the differences in density between the intraperitoneal fluid and the displaced liver.

(b) These changes are confirmed by tomography following the effect of total body opacification.

Fig. 3-60. Fluid lateral to the liver.

(a) Plain film visualization of the lateral margin of the right lobe (arrows) is highlighted by the differences in density between the intraperitoneal fluid and the displaced liver.

(b) These changes are confirmed by tomography following the effect of total body opacification.

Radiobiology Images Effects The Body

Fig. 3-61. Fluid lateral to the liver and spleen.

The enhancement of visualization of the liver (L) and spleen (S) during intravenous infusion of contrast medium clearly demonstrates their medial displacement in a case of ascites. Arrows point out their lateral borders. These changes help to explain the occasional plain film observation of Hellmer's sign. K = kidneys.

Hellmer Sign

ascends in the flank to the space above the dome of the liver. Pyogenic membranes may compartmentalize an abscess solely to Morison's pouch (Figs. 3-58 and 359). Characteristically, this presents as a discrete air-fluid level posteriorly at the level of the 10th to 12th ribs.

Whether further spread occurs is probably related to many factors, including particularly the rapidity with which the infection develops and the virulence of the infecting organisms. Fluid collections in the right posterior subphrenic space cannot extend medial to the cor

Recessus Subphrenic

Fig. 3-62. Right subhepatic and subphrenic abscesses.

Upright film demonstrates an abscess within Morison's pouch (single arrow) and two air-fluid levels beneath the diaphragm (arrows), representing collections in the right subphrenic spaces over the dome of the liver.

Fig. 3-62. Right subhepatic and subphrenic abscesses.

Upright film demonstrates an abscess within Morison's pouch (single arrow) and two air-fluid levels beneath the diaphragm (arrows), representing collections in the right subphrenic spaces over the dome of the liver.

Gas The Subphrenic Space

Fig. 3-63. Right perihepatic fluid following a perforated duodenal ulcer.

Following the introduction of water-soluble contrast medium in a nasogastric tube, CT demonstrates a gas bubble in the region of the porta hepatis (arrow) and high-density contrast material in the right perihepatic space (asterisks).

Fig. 3-63. Right perihepatic fluid following a perforated duodenal ulcer.

Following the introduction of water-soluble contrast medium in a nasogastric tube, CT demonstrates a gas bubble in the region of the porta hepatis (arrow) and high-density contrast material in the right perihepatic space (asterisks).

onary ligamentous attachments (Fig. 3-64). This is a useful landmark, then, in the distinction from other processes.49,50 Direct passage from the right subphrenic space across the midline to the left subphrenic space is prevented by the falciform ligament.

These dynamics of flow explain the incidence and location of intraperitoneal abscesses reported empirically in large clinical series. The frequency of subphrenic and subhepatic abscesses is two to three times greater on the right than on the left,49 and the most common site is

Perihepatic Abscess

Fig. 3-64. Right subphrenic abscess.

Gadolinium-enhanced T1-weighted SGE MR image demonstrates a right perihepatic abscess (a) with a characteristic thick enhancing inflammatory capsule (arrowheads). (Reproduced from Semelka et al.43)

Fig. 3—65. Right subphrenic abscess, following perforation of a duodenal ulcer.

CT demonstrates a large gas-containing abscess (A) compressing the right lobe of the liver. It is demarcated by the attachments of the falciform ligament anteriorly (arrow) and the superior coronary ligament posteriorly (curved arrow).

Subphrenic Abscess

Fig. 3—66. Right subphrenic abscess

(a and b) CT at two different levels demonstrates a large subphrenic abscess with gas bubbles. Anteriorly, it is marginated by the falciform ligament (arrow) and posteriorly by the right coronary ligament at the bare area of the liver (arrowhead). (b) The right subphrenic abscess is divided into a large anterior one (A) and a small posterior one (P). A small left subphrenic abscess is seen to the left of the falciform ligament (open arrow).

Fig. 3—66. Right subphrenic abscess

(a and b) CT at two different levels demonstrates a large subphrenic abscess with gas bubbles. Anteriorly, it is marginated by the falciform ligament (arrow) and posteriorly by the right coronary ligament at the bare area of the liver (arrowhead). (b) The right subphrenic abscess is divided into a large anterior one (A) and a small posterior one (P). A small left subphrenic abscess is seen to the left of the falciform ligament (open arrow).

Localized Subhepatic CollectionSubphrenic Gas

Fig. 3—67. Right subphrenic abscess.

CT demonstrates a large gas-containing abscess (A) in the right subphrenic space over the dome of the liver (L) with a thick enhancing rim. A small pleural effusion (E) extends into the medial costophrenic angle.

(Courtesy of Gary Ghahremani, M.D., Evanston Hospital, Evanston, IL.)

Fig. 3—67. Right subphrenic abscess.

CT demonstrates a large gas-containing abscess (A) in the right subphrenic space over the dome of the liver (L) with a thick enhancing rim. A small pleural effusion (E) extends into the medial costophrenic angle.

(Courtesy of Gary Ghahremani, M.D., Evanston Hospital, Evanston, IL.)

Morison's pouch.9 Abscesses localized solely to the right anterior subhepatic space are relatively uncommon. Abscesses of Morison's pouch and the right subphrenic space often coexist. Clinical evidence of abscesses limited to the right subphrenic space, however, is not uncommon, but it can be assumed that some contamination of the right posterior subhepatic space had already occurred, perhaps manifested only by some residual inflammatory adhesions.

Hydrostatic Considerations. In addition to the anatomic pathways and action of gravity, variations in intraperi-toneal pressure also determine the distribution of peritoneal fluid. Egress from the pelvis upward is not a function simply of overflow. Fluid surmounts the sacral promontory and flank muscles to extend upward, whether the patient is horizontal or erect. Autio51 first documented the intraperitoneal extension of radiographic contrast medium into the upper abdominal re cesses even in the erect position. Ten milliliters of oily contrast medium were introduced into the ileocecal, paracecal, and paraduodenal regions of 38 patients in connection with appendectomy or cholecystectomy. Although the oil derivative tended to fragment, it had an advantage in that it persisted in the peritoneal cavity for at least 3 days before being absorbed. It was therefore possible to see that its distribution on the first day, when the patient was supine, was the same as that on later days, when the patient was erect for lengthy periods of time, and achieved its final disposition within 3 hours of insertion. The contrast medium moved both down into the pelvis and up into the subphrenic space via the two-way avenue of the right paracolic gutter.

The hydrostatic pressure of the contents of the abdominal cavity together with the flexibility of a portion of the abdominal wall determine, for the most part, the pressure within the abdominal cavity. Overholt52 demonstrated in animals that the hydrostatic pressure in the subdiaphragmatic region is lower than that elsewhere in the abdomen and that the pressure varies with respiration. The intraperitoneal pressure in the upper abdomen is subatmospheric and decreases further during inspiration. This negative subdiaphragmatic pressure and its relation to breathing are maintained in the horizontal or erect position. This is explained by the outward movement of the ribs during inspiration, which enlarges the space in the upper abdomen more than it is decreased by the descent of the diaphragm. Salkin53 subsequently confirmed these observations in humans, noting in a series of 50 cases that most showed an intraperitoneal pressure of from 0 to - 30 mm H20 and that pressure is less in the epigastrium than in the hypogastrium. Drye54 recorded that in the supine position intraperi-toneal pressure averages 8 cm and in the upright position pressure in the lower abdomen is almost three times as great as in the supine position. These pressure differences with positional and respiratory variations have been confirmed by others. Hydrostatic pressure differences between the lower and upper abdomen are capable then, even in the upright position, of conveying infected material.

Fluid introduced into the right supramesocolic area follows similar pathways.6 Preferential flow is directly into Morison's pouch, with progression to the right sub-phrenic space and, via the right paracolic gutter, to the pelvis. In 1940, Mitchell,11 using sequential injections of barium emulsions in infant cadavers, concluded that ex-udates do not progress directly from beneath the liver to the subphrenic area but first follow a circuitous route over and ventral to the proximal transverse colon to contaminate the right infracolic space. Although many of his basic observations have been subsequently confirmed, he incorrectly concluded that the right paracolic gutter is not the major path of communication by which infection spreads to and from the upper and lower peritoneal compartments. It was not until the development of peritoneography that the effects of intraabdominal pressure gradients and body movements in vivo on the flow of fluid were accurately observed radiologically.6,14

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Responses

  • belba galbassi
    Is pouch of douglas viewable on pelvic ct?
    3 years ago

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