Patient with Acute Abdominal Pain

I The Case of Melissa Stonegrave

Checklist:

Acute Abdomen

• Is the patient standing up or positioned on the left side, and is the x-ray beam horizontal?

• Do you see air outside of the gastrointestinal tract?

• Is the air within the gastrointestinal tract normally distributed?

• Are "sentinel loops" with air-fluid levels of differing height present?

• Are there characteristic calcifications present?

Mutiny in the Belly

The paramedics found Melissa Stonegrave (51) helpless on a park bench. Passersby had noticed her as she was lying on her side wincing and calling for help. The paramedics noted that she complained of severe abdominal pain. In the emergency room she was carefully examined. A nasogastric tube was inserted because the patient had vomited. Giufeng is looking through some rather boring cases of the teaching file when x-ray technician Thomas brings Mrs. Stonegrave's radiographs over from the emergency room for her to review. Giufeng puts the chest radiograph on the viewbox first, but sees nothing abnormal and puts it to the side. Pulmonary problems such as a basal pneumonia as a cause of her symptoms do not seem to be present. She grabs the abdominal radiograph and begins a careful analysis (Fig. 9.3).

I The Case of Melissa Stonegrave

Free Intraperitoneal Air Causes

Fig. 9.3 Have a look at the abdominal radiograph of Melissa Stonegrave. Which finding grabs your attention right away?

• What is your diagnosis?

Free intraperitoneal air: In case of free intraperitoneal air, the perforation of a hollow organ such as the stomach, the duodenum (in ulcer disease), or the large bowel (for example in diverticulitis), or a traumatic perforation must

Fig. 9.3 Have a look at the abdominal radiograph of Melissa Stonegrave. Which finding grabs your attention right away?

be considered (Fig. 9.4). It may, however, also be residual air after a surgical intervention in the abdomen, which may persist for days and weeks.

Air in the retroperitoneum: Retroperitoneal air is much less frequent and occurs, for example, in perforations of retroperitoneal bowel segments such as the duodenum, colon, or rectum (Fig. 9.5). It can also occur in severe infections with gas-forming bacteria, e.g., emphysematous pyelonephritis in diabetic patients.

Air in the bowel wall: Air in the bowel wall can be observed in pneumatosis intestinalis (Fig. 9.6a, b), a benign asymptomatic condition, or in the late phase of bowel ischemia (Fig. 9.6c) that goes along with severe abdominal pain. In extreme cases the air reaches the portal venous system of the liver via the mesenteric veins (Fig. 9.6d). In the olden days this used to be a "signum mali ominis," an ominous sign indicating a deleterious course of the disease. In times of ubiquitous CT, the sign is much more often seen and is fortunately less prognostic.

Bowel obstruction (mechanical ileus): Also termed mechanical or dynamic ileus, this condition is characterized by a mechanical obstruction of the intestinal lumen (Fig. 9.7a). In the small bowel, postoperative fibrous bands, so-called adhesions, are the most frequent cause of obstruction followed by incarcerated hernias (inguinal, femoral, umbilical, and incisional). In children an intussusception may be the culprit. Gallstones that have perforated into the bowel lumen (Fig. 9.7b) may be a cause of obstruction that can be directly visualized on the radiograph. In the large bowel, colorectal carcinomas, volvulus of the

I Free Intraperitoneal Air

I Free Intraperitoneal Air

Colon Obstruction Left Side

Fig. 9.4a This upright chest radiograph shows an evident pocket of air underneath the right hemidiaphragm. The lungs themselves are clear. There is a small right-sided pleural effusion. This patient was brought into the emergency unit with an acute abdomen due to a gastric perforation. b In another patient positioned on the left side and imaged with a horizontal x-ray beam, an air depot is present between the liver, the diaphragm, and the abdominal wall (arrow). This patient underwent abdominal surgery two days before. An upright radiograph was still impossible to obtain. The air in some small-bowel loops indicates an additional disturbance of the intestinal peristalsis. c Free air in the abdomen is not quite that easy to diagnose by CT—if free fluid is also present the air-fluid levels are reliable proof (arrow).

Fig. 9.4a This upright chest radiograph shows an evident pocket of air underneath the right hemidiaphragm. The lungs themselves are clear. There is a small right-sided pleural effusion. This patient was brought into the emergency unit with an acute abdomen due to a gastric perforation. b In another patient positioned on the left side and imaged with a horizontal x-ray beam, an air depot is present between the liver, the diaphragm, and the abdominal wall (arrow). This patient underwent abdominal surgery two days before. An upright radiograph was still impossible to obtain. The air in some small-bowel loops indicates an additional disturbance of the intestinal peristalsis. c Free air in the abdomen is not quite that easy to diagnose by CT—if free fluid is also present the air-fluid levels are reliable proof (arrow).

I Air in the Retroperitoneum

Retroperitoneal Air RayAbdomen Xray With Short Scale Contrast

Fig. 9.5a This abdominal radiograph shows the contour of the iliopsoas muscle (short arrows) and the right kidney (long arrows) extremely well, much better than normal. They are outlined by air that originated from a traumatic rupture of the duodenum. The colon is filled with some water-soluble contrast from a previous enema. b To confirm the diagnosis, this CT was windowed so the difference between fat (as it is seen in the subcutaneous tissues) and air (as it is present around the kidney) is amplified.

Fig. 9.5a This abdominal radiograph shows the contour of the iliopsoas muscle (short arrows) and the right kidney (long arrows) extremely well, much better than normal. They are outlined by air that originated from a traumatic rupture of the duodenum. The colon is filled with some water-soluble contrast from a previous enema. b To confirm the diagnosis, this CT was windowed so the difference between fat (as it is seen in the subcutaneous tissues) and air (as it is present around the kidney) is amplified.

I Air in Bowel Wall a a

Air Colon Wall

Fig. 9.6a In the right upper abdomen several layers of air (arrows) are present around the intestinal lumen. b The CT confirms the presence of air in the bowel wall (arrows). This patient had an acute myelogenous leukemia (AML) but no intestinal symptoms whatsoever at that time and later. This turned out to be pneumatosis intestinalis. c The CT section in another patient with severe abdominal pain displays a marked thickening of the bowel wall with small air deposits in it—much like a "string of beads" (white arrows): This bowel segment is gangrenous.

Fig. 9.6a In the right upper abdomen several layers of air (arrows) are present around the intestinal lumen. b The CT confirms the presence of air in the bowel wall (arrows). This patient had an acute myelogenous leukemia (AML) but no intestinal symptoms whatsoever at that time and later. This turned out to be pneumatosis intestinalis. c The CT section in another patient with severe abdominal pain displays a marked thickening of the bowel wall with small air deposits in it—much like a "string of beads" (white arrows): This bowel segment is gangrenous.

Signs And Symptoms Ascites

In addition, thin rims of ascites are seen around the liver and also around the spleen. By the way: The contrast defect in the vena cava (black arrow) is not a thrombus but is a result of laminar flow! Blood rich with contrast medium from the kidneys flows along uncontrasted blood from the lower extremities. d Once there is air in the necrotic bowel wall, it can also enter the mesenteric veins and eventually the hepatoportal system (arrows).

sigma (Fig. 9.7c) or cecum and diverticulitis must be excluded as the cause of the ileus. Enemas with water-soluble contrast media are essential in the radiographic differentiation of these entities in the large bowel. CT of the abdomen with multiplanar 3D image reconstructions on a workstation can help determine the point of obstruction as well as provide clues to the underlying cause.

Paralytic ileus: The paralytic ileus may be due to a number of different conditions (Fig. 9.8). It is also the pathophysio-logical end point of a persisting untreated bowel obstruc tion. It may be seen after surgical interventions in the abdomen, after abdominal trauma, and in electrolyte imbalances, sepsis, peritonitis, or infiltration of the mesentery by tumor.

Acute pancreatitis: An acute pancreatitis is not normally diagnosed on the abdominal radiograph. The signs of recurring or chronic pancreatitis may, however, be visible and point the diagnostic work-up in the right direction (see Fig. 9.2d).

I Mechanical Ileus a Colon carcinoma a Colon carcinoma

Sentinel Loop Sign

Fig. 9.7 a Numerous sentinel loops with air-fluid levels of varying heights indicate a mechanical (dynamic) ileus. The colon is essentially free of air. This was an obstruction due to a colon carcinoma. b Airis seen intheduodenumand proximal jejunum, almost none in the colon (left). This looks like a jejunal obstruction. The reason is a giant gallstone that has found its way into the jejunum. Can you see it above the left iliac crest? On its way into the jejunum the gallstone has created a communication (right) through which air seeps into the biliary system. Note the air-filled common bile duct coursing toward the distended duodenum! Air may also be seen in the biliary tract after the rather frequent therapeutic dilation of the papilla of Vater and must be differentiated from air in the portal system as an ominous sign of bowel ischemia. c In another patient an extremely dilated and air-filled bowel loop (left) is identified as sigmoid colon owing to its location and the obvious haustration. The colon is nicely outlined by air; the rectum shows no air at all. This is a sigmoid volvulus, a torsion of the sigma around its mesenteric root. The result is, of course, mechanical bowel obstruction. The configuration of the bowel in this entity is reminiscent of the underside of the "bean" that helps us through many a day: It is called the "coffee-bean sign." The volvulus is confirmed with the help of an enema with water-soluble contrast. We see a "bird's-beak" like configuration of the contrast column at the rectosigmoidal transition (right). ►

b Gallstone b Gallstone

Coffee Bean Volvulus

I Mechanical Ileus c Volvulus

Picture Patient Ileus
I Paralytic Ileus
Paralytic Ileus

Fig. 9.8 In this cancer patient the diffuse spread of cancer in the retroperitoneum has necessitated stenting of both ureters to keep urine flowing from kidneys to the bladder. Now a paralytic ileus has developed on top of that: distended bowel loops with air-fluid interfaces that tend to have the same levels in one loop and that seem to be present everywhere. Note: Paralytic ileus is usually diagnosed with a stethoscope! Imaging is not really needed here.

Fig. 9.8 In this cancer patient the diffuse spread of cancer in the retroperitoneum has necessitated stenting of both ureters to keep urine flowing from kidneys to the bladder. Now a paralytic ileus has developed on top of that: distended bowel loops with air-fluid interfaces that tend to have the same levels in one loop and that seem to be present everywhere. Note: Paralytic ileus is usually diagnosed with a stethoscope! Imaging is not really needed here.

• Diagnosis: Giufeng has not found any free air in the peritoneum or retroperitoneum of Mrs. Stonegrave. However, she thinks that the distribution of air in the intestines is grossly abnormal. The colon is completely free of air, while the small bowel shows many sentinel loops with air-fluid levels of differing heights. It is quite clear to her that a mechanical bowel obstruction is present; air in the colon has been absorbed or passed. Giufeng diagnoses a dynamic, mechanical ileus on the basis of an obstruction of the small bowel or the proximal colon. As it turns out, Melissa Stonegrave had undergone a complicated cholecystectomy a few years earlier. During surgery, adhesions were found to be the cause of the small-bowel obstruction.

f Most bowel obstructions are actually treated conservai tively with a nasogastric tube and observation. In fact, CTallowsusto stratify patients into a surgical versus a nonsurgical group by detecting the presence or absence of ischemia, portal venous gas, extraluminal disease, etc., which clearly represents an advance over the olden times when the clinical picture (signs of sepsis, shock, acidosis, etc.) was all we had in addition to the radiograph.

f Free intraperitoneal air and an ileus are best diagnosed on i an abdominal radiograph with the patient standing or positioned on the left side and a horizontal x-ray beam. The infrequent retroperitoneal air and the cause of a mechanical bowel obstruction are often better appreciated on CT. Free fluid is detected most rapidly by ultrasound. Make a note of that: It is not always the most expensive modality that gives you the crucial information!

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