Several different abdominal drainage systems are used postoperatively or in the setting of interventional procedures. Besides carrying out interventional procedures, the tasks of the radiologist include checking the position of drainage systems and detecting possible complications (e. g., perforation).

Classification by Drain Type

Bloody Drainage

Some drains are placed to allow the prompt detection of bleeding and provide for drainage of blood and lymph. The Robinson drain and Honig drain are most commonly used. These drains are usually removed on the second postoperative day.

Drainage of Anastomoses

Drains are placed close to surgical anastomoses to allow for prompt drainage of anastomotic leaks. The absence of drainage confirms that the anastomosis is secure. These drains are generally removed on the sixth postoperative day. Not all anastomoses are drained. For example, the mobility of a small bowel anastomosis would limit the options for tube placement, whereas a deeply placed rectal anastomosis would be amenable to drainage. Most anastomotic drains are made of soft material (Penrose, Easy-Flow).

Drainage in Septic Surgery

Honig and Robinson drains are preferred for the drainage of abscesses.

Dwell Time

The timing of drain removal depends on the volume and quality of the drainage. With a pancreatic anastomosis, for example, the drain should be removed when the output falls below 50 mL/day. In the case of an infection, the drain should be left in situ for a longer time.

Small-bore feeding tubes for enteral nutrition have a diameter of 6–8F (1F = 0.3 mm) while large-bore tubes may be as large as 18F. Larger tubes are marked with radio-paque stripes to aid localization. Enteral feeding in intensive care unit (ICU) patients can be done through a nasoenteral tube (gastric, duodenal, or jejunal), percutaneous gastrostomy, or catheter jejunostomy.

Stomach Tube

There is controversy as to the need for biliary drainage in cases where the common bile duct has been opened. Most authors advocate drainage because the rate of complications is higher without it.

The Kehr T-drain is widely used for biliary drainage. Straight, single-lumen tubes with side openings can also be used. The drain is removed between 2 and 3 weeks postoperatively.

Examination Technique

T-tube cholangiography is usually performed on the sixth or seventh postoperative day. A plain radiograph is taken, and then contrast medium is instilled by manual retrograde injection through the T-tube to opacify the biliary tract including the intrahepatic ducts. Approximately 10 mL of undiluted, water-soluble, nonionic, iodinated contrast medium should be used for the detection of peripheral leaks.

Complications

Possible complications are residual stones in the common duct, obstruction of the T-drain by inspissated biliary fluid, and blood clots or strictures of the bile duct at the insertion site of the T-drain, which may necessitate reoperation.

Patients occasionally develop postoperative external fistulas through the skin or internal fistulas that communicate with the duodenum, colon, or stomach. Most of these fistulas will close spontaneously and without sequelae in the absence of a distal biliary tract obstruction or biliary tract injury.

Perforation during stenting of the common duct or papilla may lead to cholascos (escape of bile into the peritoneal cavity) with subsequent biliary peritonitis.

Other complications of biliary tract surgery include hemorrhage, suture-line leak, and subhepatic fluid collections including abscess or empyema formation, which are investigated by CT (see sections below on Biliary Tract Surgery and Cholecystectomy).

Percutaneous Nephrostomy and Ureteral Stenting

Percutaneous nephrostomy (PCN) is the procedure of choice for the decompression of hydronephrosis or for establishment of access for nephroscopy, lithotripsy, or antegrade ureteral stenting. Various techniques employ a fine percutaneous needle to catheterize the renal pelvis through a calyx under local anesthesia (using sono-graphic and/or fluoroscopic guidance). The tract is dilated, and a drainage catheter (12–16F) or ureteral stent is introduced.

Complications. Potential complications are a bleeding arteriovenous (AV) fistula and the development of a false aneurysm or urinoma. Suspected complications should be investigated by ultrasonography (duplex if necessary) and by CT.

Bladder Catheterization

Catheters can be introduced into the bladder by the suprapubic or transurethral route. Bladder catheterization is essential for monitoring and adjusting the fluid balance in ICU patients.

Transurethral catheterization is technically easy to perform but carries a higher risk of infection and late sequelae (strictures, epididymitis) than suprapubic bladder aspiration. The latter procedure is done on a dis-tended bladder under ultrasound guidance using a special disposable instrument set.

Correct catheter placement can be confirmed by fluoroscopically guided contrast instillation. Imaging should be done in two planes (supine and lateral oblique projections).

Complications. Any suspected complications should be investigated by a CT study that includes a delayed series 10 min after IV contrast administration, or by ultrasound scanning of the well-distended bladder. Contrast medium should be diluted 1:20 for intravesical instillation.

Postoperative intra-abdominal fluid collections do not always signify an abscess or hemorrhage. Fluid retention lasts until postoperative day 4 in ca. 20% of patients, day 8 in 6%, and day 12 in ca. 2%. Typically these (physiologic) fluid collections are crescent-shaped, their shape conforms to surrounding structures, and they occur in preexisting spaces or recesses, where they become spontaneously reabsorbed by the peritoneum.

Reflex or pharmacologically induced gastrointestinal atony (functional or adynamic ileus) consistently occurs during the first two postoperative days, especially after operations that involve the bowel. The paralysis results from premedication and general anesthesia and from the surgical procedure itself (intraoperative therapy, autonomic response).

Usually, peristalsis does not resume until the third postoperative day. The resumption of peristalsis usually occurs spontaneously. Thus, bowel distention is consistently encountered during the immediate postoperative period. It can significantly impede sonographic examination and may increase abdominal circumference in a way that mimics postoperative bleeding.

Imaging

The bowel appears moderately dilated with little or no peristalsis. There is no abrupt cutoff of the gas column, but significant gaseous distention is common. In cases of nonobstructive paralysis, the dilatation involves the small bowel and the ascending colon as far as the hepatic flexure. The rest of the colon has a normal caliber.

Free intra-abdominal air is a normal finding in the immediate postoperative period. It is highly variable in its duration and extent, depending on patient habitus and the nature of the surgery. The prevalence of postoperative free-air decreases with time after surgery, declining from 44% during the first 3 days to 31% by days 4–7.

The quantity of free air is highly variable. Air following a laparoscopy (insufflated CO₂) is absorbed more rapidly than after other types of surgery. Free air has been found with greater frequency and duration in thin patients, male patients, and patients with indwelling drains. Otherwise no correlation has been found between the type of surgery, patient age, and the extent of postoperative pneumoperitoneum.

Note that even patients with an anastomotic leak will not necessarily have free air at CT examination, so the exclusion of a pneumoperitoneum does not prove that the gastrointestinal tract is intact.

Diagnostic Strategy and Examination Technique

The imaging strategy will depend upon whether we must evaluate:

an extubated, mobilized patient who is a good candidate for abdominal radiography and radiographic follow-ups, or

an ICU patient who is still on mechanical ventilation; radiographs are technically difficult to perform and are rarely diagnostic in this subgroup, and primary sectional imaging studies (ultrasonography and CT) are preferred.

Plain Abdominal Radiograph

A plain abdominal radiograph is indicated in patients with symptoms of ileus and suspicion of a (new) pneumoperitoneum. It is helpful in identifying residual contrast medium from prior examinations and differentiating it from contrast extravasation.

Ideally, plain abdominal radiographs should be taken in two planes, although this is usually not practical in the ICU:

Initial anteroposterior (AP) supine radiograph using a grid cassette (35 × 43 cm) and low kilovoltage (70 kV) demonstrates organs and soft tissues.

Left lateral decubitus AP radiograph using a grid cassette (35 × 43 cm) and high kilovoltage (125 kV) detects air–fluid levels, assesses intraluminal gas distribution, and detects free air and atypical gas collections (pneumatosis, pneumobilia, etc.). As an alternative, the second view may be a supine cross-table projection with a laterally mounted cassette.

Ultrasonography

Owing to its convenience and availability, ultrasonography is the primary imaging study for the detection of free fluid or suspected fluid collections.

Even small amounts of intra-abdominal free fluid can be detected with high sensitivity (> 90%). Sites of predilection for fluid collections are the Morison pouch (hepatorenal recess) and the lesser pelvis.

As to the limitations of ultrasonography, (small) fluid collections due to leaks cannot be distinguished qualitatively from postoperative reactive or lymphogenous fluid collections that are still within normal limits, or from preexisting ascites. Intraluminal bowel hemorrhages are also difficult to detect on ultrasound scans.

An important advantage of ultrasonography (as an adjunct to CT) is its ability to distinguish an abscess from a fluid-filled bowel loop based on the real-time evaluation of peristalsis.

Radiography

Radiographic follow-ups after oral contrast administration (water-soluble Gastrografin) for detecting leaks or obstructions are rarely practiced nowadays, especially in ICU patients.

Computed Tomography

CT is the imaging modality of choice for almost all postoperative complications (bleeding, abscess, obstruction, leakage).

Oral contrast administration? The bowel can be opacified in the subacute stage with ca. 1 L of a diluted water-soluble contrast medium, administered orally, to distinguish fluid-filled bowel loops from extraintestinal collections. Oral contrast administration is often not possible during the acute stage and will only cause needless delay.

In principle, however, an abscess or bowel obstruction can be diagnosed even without IV contrast. Thus, a contraindication to contrast medium (renal failure) does not justify withholding a CT examination.

CT or ultrasonography? CT is preferred for the diagnosis of intra-abdominal abscess and for locating the focus in postoperative sepsis. Although ultrasound scanning is advantageous in its rapid availability (e. g., in the supine ICU patient), its technical limitations and frequent unfavorable acoustic conditions favor early evaluation by CT. Both modalities can also be used successively and in a complementary fashion.

While intrasplenic, intrahepatic, subhepatic, and subphrenic abscesses can usually be diagnosed with ultra-sonography, CT is better for detecting retroperitoneal abscesses and abscesses located between bowel loops or within the lesser pelvis.

Finally, ultrasonography and CT are equally useful in directing diagnostic or therapeutic needle aspiration (and drainage) and for distinguishing an abscess from noninfectious lesions such as pancreatic pseudocyst, hematoma, bilioma, seroma, aseptic necrosis, postoperative fluid collection, or an unexpected tumor.

Pharmacologic therapy (vasoconstriction by IA vasopressin infusion) is mainly of historical interest but may still be tried in rare cases where a bleeding site cannot be identified.

Scintigraphy

Radionuclide imaging techniques have become much less important owing to the broad and rapid availability of sectional imaging modalities. Only the technetium-labeled red blood cell scan still has a significant role in detecting intraluminal bleeding at rates up to 0.1 mL/min. As with other modalities, intermittent bleeding is frequently occult on radionuclide scans. Unlike conventional and CT angiography, scintigraphy is not useful for acute diagnosis.

Fig. 5.1 a–c Variable CT appearance of hematomas.

a Hematoma appearing as bloody ascites (note the density and sedimentation effect).

b Hematoma appearing as a loculated, inhomogeneous, hyperdense fluid collection following multiple slow bleeds.

c Hematoma appearing as a homogeneous fluid collection with a layer of sedimentation after a single profuse bleed.

Free hemorrhage. Even with CT, it can be difficult to distinguish free intraperitoneal bleeding from an abscess. CT will sometimes show fine sedimentation in the posterior dependent recesses as evidence of bleeding in preexisting ascites.

Sepsis describes a systemic response to an infectious focus located in the body (not necessarily intra-abdominal). Any monitoring change noted in the postoperative patient may be an initial sign of early sepsis: cardiovascular parameters, blood gas analysis, ventilation, laboratory values, body temperature, or general status.

Common findings in postoperative sepsis are paralytic ileus with distention of the small and large bowel and diffuse subcutaneous edema. The patient is febrile and, when conscious, complains of nausea and vomiting. A precipitous fall in white blood count (e. g., from 13 000 to 3000) is indicative of gram-negative sepsis.

Fig. 5.2 a, b Extensive intraperitoneal (mesenteric) hematoma.

Shown here with a sedimentation layer and bloody ascites.

Fig. 5.3 a, b Extensive retroperitoneal bleeding from the aorta with displacement of the left kidney (arrow).

Note in b the sedimentation of contrast medium in the aneurysmatic aorta (arrowhead) due to impaired left ventricular function.

Fig. 5.4 a, b Subcapsular hematoma in the liver.

A subcapsular hematoma is impressing on the (soft) liver tissue. Patient presented with a sudden decrease of hemoglobin level 8 days after partial gastrectomy.

Peritonitis is defined as an inflammatory reaction of the peritoneum to pathogenic stimuli such as bacteria, viruses, and chemical agents.

Classifications

Primary peritonitis (hematogenous, lymphogenous, or luminal invasion/contamination) is distinguished from secondary peritonitis due to a perforated hollow viscus and from tertiary or persistent peritonitis. While secondary peritonitis is treated by surgical eradication of the focus and pharmacologic therapy serves only as an adjunct, the causal treatment for primary peritonitis is antibiotic pharmacotherapy.

Surgical treatment is appropriate for primary peritonitis only in cases that have not responded to antibiotics. Therapeutic options are debridement and copious irrigation of the abdominal cavity to reduce microorganism counts.

For the prevention of persistent “tertiary” peritonitis and intra-abdominal abscess formation (ca. 20% incidence after secondary peritonitis), it is generally agreed that eradication of the focus should be followed by additional surgical measures based on the principle of “need-oriented relaparotomy” (= reoperation prompted by a deterioration of the patient’s general condition).

Postoperative peritonitis, which most commonly results from anastomotic leak, affects a patient that is already traumatized by the previous operation and is subject to an “acute-phase response” (with systemic activation of mediators). Today it is believed that the acute-phase 20% incidence after secondary peritonitis), it is generally agreed that eradication of the focus should be followed by additional surgical measures based on the principle of “need-oriented relaparotomy” (= reoperation prompted by a deterioration of the patient’s general condition). Response combined with the infectious “second hit” may initiate the development of multiorgan dysfunction syndrome (MODS). The mortality rate of this condition, at 50%, is substantially higher than that of a primary hollow viscus perforation.

The routine clinical description of “(single) quadrant peritonitis” or “multiquadrant peritonitis” is based on a gross subdivision of the abdomen into four quadrants and does not follow predefined anatomical boundaries.

Clinical Aspects

Plain Abdominal Radiograph

Due to the frequency of perforation-induced peritonitis, a diagnosis of peritonitis should be considered whenever a pneumoperitoneum is found. Abdominal radiographs show generalized intestinal atony and distention with fluid levels in the small and large bowel. Specific signs of peritonitis are not seen. Displacement and obvious asymmetry of bowel loops is suggestive of an abscess.

Ultrasonography

Ultrasound reveals atonic, fluid-filled bowel loops. Free fluid is detected at sites of predilection. Attention is given to the morphology of the gallbladder (caution: cholecystitis) and to any fluid collections that are suspicious for an abscess (see below).

Computed Tomography