Extraperitoneal Perforations of the Colon and Appendix

Figure 8-45 illustrates that extraperitoneal perforations of the colon can be identified as clearly localized to the anterior pararenal space, even on plain films. The extra-peritoneal collection of mottled gaseous lucencies is oriented with a general vertical axis, medially overlaps the psoas muscle and approaches the spine, and does not obscure the flank stripe laterally. In this patient, who text continues on page 362

Flank StripeAnterior Pararenal Space Spread

Fig. 8-40. (a) Postmortem injection into the anterior pararenal space.

The collection has a generally vertical axis. Laterally, the lucent flank stripe is intact (white arrows). Medially, spread approaches the spine over the psoas muscle. Superiorly, it follows the obliquity of the kidney, and there is extension to the bare area of the liver at the site of reflection of the coronary ligament (black arrows). (From Meyers et al.12)

(b) Diagram showing the characteristic spread and configuration of extraperitoneal fluid and/or gas collections in the anterior pararenal space (APS).

Superiorly, there is continuity to the bare area of the liver at the reflections of the right coronary ligament (CL). P = psoas muscle margin.

Configuration of collection within the posterior pararenal space (PPS) on the opposite side is shown for comparison.

Fig. 8—41. Anterior pararenal abscess, secondary to duodenal perforation, extending cephalad to bare area of liver.

CT in a patient with abdominal pain and fever following an endoscopic papillotomy shows air in the biliary tract and a gas-containing collection, secondary to perforation of the descending duodenum, in the anterior par-arenal space, extending cranially to the bare area (arrows). K = kidney; C = inferior vena cava. (Reproduced from Arenas et al.66)

Fig. 8-42. Fluid in the anterior pararenal space.

Direct coronal CT section reveals a fluid collection (F) in the left anterior pararenal space (arrows) with a vertical axis and medial extension inferiorly. The outlines of the kidney and of the psoas muscle (PS) are preserved (black arrows), and the flank fat (3) of the posterior pararenal space is not infiltrated. The descending colon is not visible since it has been displaced ven-trally. LK = left kidney; IL = iliacus muscle.

(Reproduced from Feldberg.17)

Perirenal FatPerirenal Pararenal FatExtraperitoneum Pararenal Fascia

Table 8-1. Radiologic criteria for localizing extraperitoneal effusions

Radiologic features

Anterior pararenal space

Perirenal space

Posterior pararenal space

Perirenal fat and renal oudine Axis of density

Kidney displacement

Psoas muscle oudine

Flank stripe

Hepatic and splenic angles Displacement of ascending or descending colon Displacement of descending duodenum or duodenojejunal junction

Preserved Vertical

Lateral and superior

Preserved

Preserved Obliterated Anterior and lateral

Anterior

Obliterated Vertical (acute) Inferomedial (chronic) Anterior, medial, and superior Upper half obliterated

Preserved

Obliterated

Lateral

Anterior

Preserved Inferolateral

(parallel to psoas margin) Anterior, lateral, and superior

Obliterated in lower half or throughout Obliterated

Preserved or obliterated Anterior and medial

Anterior

Anterior Pararenal Space

Fig. 8—44. Anterior pararenal space blood from leaking abdominal aortic aneurysm.

CT scans demonstrate that the extravasate is localized to the left side at the level of the renal hila (a) and extends across the midline at the level of the lower renal poles (b). Retroaortic and perirenal reaction are evident. (Courtesy of Michiel Feldberg, M.D., University of Utrecht, The Netherlands.)

Fig. 8—44. Anterior pararenal space blood from leaking abdominal aortic aneurysm.

CT scans demonstrate that the extravasate is localized to the left side at the level of the renal hila (a) and extends across the midline at the level of the lower renal poles (b). Retroaortic and perirenal reaction are evident. (Courtesy of Michiel Feldberg, M.D., University of Utrecht, The Netherlands.)

Fig. 8—45. Perforation of the hepatic flexure.

Mottled lucent areas on the right represent collections of gas extending medially over the psoas muscle and approaching the spine. The flank stripe is intact. These changes localize the extraperitoneal gas to the anterior pararenal space.

Hepatic Flexure Characteristic

developed fever after numerous scattered polyps were removed by colonoscopic cautery, the characteristic findings localize the site of perforation to the ascending colon.

Abscesses secondary to perforated lesions of the ascending or descending colon are localized by the characteristic fascia] boundaries68 (Figs. 8-46 through 8-48).

The appendix in an ascending retrocecal position is frequently an extraperitoneal structure.69 Perforation then leads to an abscess, which may be localized within the right anterior pararenal space18,70 (Fig. 8-49).

Because the structures and connective tissue behind the anterior pararenal space are relatively unyielding, massive accumulations within it tend to distend the space anteriorly, bulging forward into the peritoneal cavity and displacing small intestinal loops. Figure 8-50 illustrates a huge abscess originating from a perforated extraperitoneal appendicitis. Its dimensions in an anterior-posterior plane approach its vertical extent from the cecal area to the transverse colon.

In children, extraperitoneal appendicitis and its associated abscess within the anterior pararenal space commonly produce pressure on the right ureter after it has emerged from the cone of the renal fascia. This typ-

Picture Soft Tissure Colon

Fig. 8-46. Left anterior pararenal space inflammatory changes secondary to diverticulitis of the descending colon.

Soft-tissue stranding through the anterior pararenal fat (arrow) adjacent to the descending colon (C) is accompanied by reactive thickening of the fascia.

(Courtesy of Jay P. Heiken, M.D., Mallinckrodt Institute of Radiology, St. Louis, MO.)

Fig. 8-46. Left anterior pararenal space inflammatory changes secondary to diverticulitis of the descending colon.

Soft-tissue stranding through the anterior pararenal fat (arrow) adjacent to the descending colon (C) is accompanied by reactive thickening of the fascia.

(Courtesy of Jay P. Heiken, M.D., Mallinckrodt Institute of Radiology, St. Louis, MO.)

ically occurs at the L5 or lumbosacral level, producing localized obstruction and hydronephrosis (Fig. 8-51). In adults, similar changes may be due to perforated carcinoma or diverticulitis of the colon but more frequently are secondary to granulomatous ileocolitis71 with extension of the infection into the anterior pararenal space (Fig. 8-52). Indeed, this localization explains the ureteral complications of Crohn's disease.

I have confirmed by postmortem injections the anatomic continuity of the right anterior pararenal space with the nonperitonealized bare area of the right lobe of the liver (Fig. 8-40) at the site of reflection of the right coronary ligament.12 This pathway permits the spread of disease from extraperitoneal perforations of the bowel precisely to the bare area of the liver24 (Fig. 8-53).

Extraperitoneal Perforation

Fig. 8-47. Left anterior pararenal space abscess secondary to a perforated diverticulum of the mid-descending colon.

The gas-producing infection has coalesced deep to the peritoneum between the anterior renal fascia and the lateroconal fascia (arrows).

Fig. 8-47. Left anterior pararenal space abscess secondary to a perforated diverticulum of the mid-descending colon.

The gas-producing infection has coalesced deep to the peritoneum between the anterior renal fascia and the lateroconal fascia (arrows).

Ascending Colon Anterior

Fig. 8-48. Left anterior pararenal abscess following left hemicolectomy.

The gas-producing infection is bounded by thickened anterior renal (arrow) and lateroconal fascia.

Fig. 8-48. Left anterior pararenal abscess following left hemicolectomy.

The gas-producing infection is bounded by thickened anterior renal (arrow) and lateroconal fascia.

Lateroconal Fascia

Fig. 8-49. Anterior pararenal phlegmon secondary to extraperitoneal appendicitis.

CT shows infiltrate in right anterior pararenal space (1) secondary to an inflamed appendix in an ascending retrocecal position. There is thickening of the lateroconal and anterior renal fasciae (arrows). The ascending colon (AC) shows bowel wall thickening. (Reproduced from Feldberg.17)

Fig. 8-49. Anterior pararenal phlegmon secondary to extraperitoneal appendicitis.

CT shows infiltrate in right anterior pararenal space (1) secondary to an inflamed appendix in an ascending retrocecal position. There is thickening of the lateroconal and anterior renal fasciae (arrows). The ascending colon (AC) shows bowel wall thickening. (Reproduced from Feldberg.17)

Fig. 8—50. Large anterior pararenal space abscess originating from extraperitoneal appendicitis.

Barium enema. Note deformity of the medial contour of the cecum and the abscess extending to the transverse colon.

(Reproduced from Meyers. )

Phlegmon Medial Xtraconal SpaceAppendicitis Radiologi

Fig. 8-51. Extraperitoneal appendicitis.

The associated abscess within the anterior pararenal space partially obstructs the right ureter (arrow).

Fig. 8-51. Extraperitoneal appendicitis.

The associated abscess within the anterior pararenal space partially obstructs the right ureter (arrow).

Acute Ileocolitis Reson

Fig. 8-52. Anterior pararenal space abscess from granulomatous ileocolitis.

(a) Barium enema reveals severe ileoileal, ileocolic, and colocolic fistulas secondary to Crohn's disease.

(b) The associated abscess within the anterior pararenal space obstructs the right ureter after it has exited from the cone of renal fascia at the level of L5-S1.

(Reproduced from Meyers.8)

Fig. 8-52. Anterior pararenal space abscess from granulomatous ileocolitis.

(a) Barium enema reveals severe ileoileal, ileocolic, and colocolic fistulas secondary to Crohn's disease.

(b) The associated abscess within the anterior pararenal space obstructs the right ureter after it has exited from the cone of renal fascia at the level of L5-S1.

(Reproduced from Meyers.8)

Extraperitoneal Colon
b
Space Anterior LiverPararenal Space

Fig. 8—53. Extension of anterior pararenal inflammation to bare area of liver.

(a) After an ileocecal resection for Crohn's disease, inflammatory changes (arrows) within the anterior pararenal space surround the anastomotic site between the ileum (I) and the ascending colon (AC).

(b) The inflammatory changes have extended cephalad within the anterior pararenal extraperitoneal space to the bare area of the liver (arrows).

(Reproduced from Meyers et al.24)

Fig. 8—53. Extension of anterior pararenal inflammation to bare area of liver.

(a) After an ileocecal resection for Crohn's disease, inflammatory changes (arrows) within the anterior pararenal space surround the anastomotic site between the ileum (I) and the ascending colon (AC).

(b) The inflammatory changes have extended cephalad within the anterior pararenal extraperitoneal space to the bare area of the liver (arrows).

(Reproduced from Meyers et al.24)

Perforation of the Duodenum

Perforation of the duodenum is usually caused by blunt trauma to the abdomen and is now being encountered as an automobile lap-belt deceleration injury. The duodenum bears the brunt of the injury because of its firm attachment, acutely angled flexures, and compression against the vertebral column. It is of interest to note that the structure derives its name from the term "dodeka-dactilon"72 by Herophilus of Chalcedon, who lived in Alexandria from 335 to 280 B.C., because it is about 12 fingerbreadths in length. Comparatively few patients are greatly inconvenienced by the original trauma. Only when the effects of the extravasation become evident do the symptoms become marked. Rupture usually occurs at the junction of the second and third portions; multiple perforations are possible, and there may be accom panying traumatic pancreatitis. Early recognition is important because unrecognized duodenal perforation has a 65% mortality rate as opposed to a 5% mortality rate in those patients operated upon within the first 24 hours after injury.73

The extraperitoneal gas with the extravasated bile and pancreatic juices is limited to the right anterior pararenal space and takes a characteristic distribution (Figs. 8-54 and 8-55). CT is considerably more sensitive than plain films in detecting the extraluminal gas74-77 (Fig. 8-56).

Figure 8-57 illustrates another striking finding. Only when the infection progresses inferiorly, below the apex of the cone of renal fascia and the limitation of the lat-eroconal fascia, can the gas proceed directly to the pro-peritoneal fat. Gaseous lucencies can then be identified in the extraperitoneal tissues, with local extension into the flank, specifically at the level of the iliac crest and

Blunt Duodenal Perforation

Fig. 8-54. Extraperitoneal perforation of the duodenum after blunt trauma.

Several gas bubbles associated with a fluid soft-tissue density are present in the right anterior pararenal space. These cause loss of the hepatic angle, but the flank stripe (arrows) is intact. The upper GI series shows medial displacement of the descending duodenum but does not demonstrate the site of extravasation.

Fig. 8-54. Extraperitoneal perforation of the duodenum after blunt trauma.

Several gas bubbles associated with a fluid soft-tissue density are present in the right anterior pararenal space. These cause loss of the hepatic angle, but the flank stripe (arrows) is intact. The upper GI series shows medial displacement of the descending duodenum but does not demonstrate the site of extravasation.

Extraperitoneal Perforation

Fig. 8-55. Extraperitoneal perforation of the descending duodenum following blunt trauma, with spread through the right anterior pararenal space.

The mottled gas shadows continue over the psoas muscle medially but do not extend into the flank fat laterally. (Reproduced from Meyers.9)

Fig. 8-55. Extraperitoneal perforation of the descending duodenum following blunt trauma, with spread through the right anterior pararenal space.

The mottled gas shadows continue over the psoas muscle medially but do not extend into the flank fat laterally. (Reproduced from Meyers.9)

Liver Abscess Mottled Gas

Fig. 8—56. Extraperitoneal perforation of the duodenum following ERCP.

(a and b) CT demonstrates gas loculations precisely within the right anterior pararenal space (black arrows). Note that a few extend into the potential space between the two layers of the thickened posterior renal fascia (white arrow). (Courtesy of Jay P. Heiken, M.D., Mallinckrodt Institute of Radiology, St. Louis, MO.)

Fig. 8—56. Extraperitoneal perforation of the duodenum following ERCP.

(a and b) CT demonstrates gas loculations precisely within the right anterior pararenal space (black arrows). Note that a few extend into the potential space between the two layers of the thickened posterior renal fascia (white arrow). (Courtesy of Jay P. Heiken, M.D., Mallinckrodt Institute of Radiology, St. Louis, MO.)

progressing cephalad. The finding is typical of gaseous spread down the right anterior pararenal compartment and is seen most commonly in perforation of the extraperitoneal duodenum.

An upper gastrointestinal series may demonstrate the perforation site (Fig. 8-57a), but not always (Fig. 8-54).

Violation of the fascial boundaries in cases of blunt retroperitoneal duodenal rupture may result in the appearance of gas surrounding the right kidney78,79 and is associated with other findings that indicate extensive retroperitoneal cellulitis. However, CT has shown that the exudate may not truly enter the perirenal space but extend from the anterior to the posterior pararenal space around the renal fascial cone.18,74

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