DOI: 10.1148/rg.263055101
RadioGraphics 2006;26:679-690
© RSNA, 2006
Review of the Abdominal Manifestations of Cystic Fibrosis in the Adult Patient1
Michael B. Robertson, MD,
Kyuran A. Choe, MD and
Patricia M. Joseph, MD
1 From the Departments of Radiology (M.B.R., K.A.C.) and Internal Medicine (P.M.J.), University of Cincinnati, 234 Goodman St, ML 0761, Cincinnati, OH 45267-0761. Presented as an education exhibit at the 2004 RSNA Annual Meeting. Received April 25, 2005; revision requested May 24 and received July 15; accepted July 20. All authors have no financial relationships to disclose.
Address correspondence to K.A.C. (e-mail: choeka{at}email.uc.edu).
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Abstract
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Cystic fibrosis is a common inherited fatal disease. As the life expectancy of affected individuals continues to increase with advances in disease management, this disease is no longer limited to the pediatric population. Currently, 40% of patients with cystic fibrosis are adults. In addition, patients may not present until adulthood and frequently have extrapulmonary symptoms. Abdominal manifestations are common and affect multiple organ systems. Hepatobiliary manifestations include fatty infiltration of the liver, gallbladder abnormalities, bile duct abnormalities, focal biliary fibrosis, and multinodular cirrhosis. Manifestations in the pancreas include acute pancreatitis, fatty replacement, calcifications, cysts, duct abnormalities, and carcinoma. Gastrointestinal manifestations include gastroesophageal reflux, peptic ulceration of the gastric and duodenal mucosa, distal intestinal obstruction syndrome, intussusception, appendicitis, fibrosing colonopathy, pneumatosis intestinalis, rectal mucosal prolapse, malignancies, and pseudomembranous colitis. Renal manifestations include nephrolithiasis, as well as secondary renal complications such as interstitial nephritis due to antibiotic therapy and amyloidosis. Awareness of these manifestations is important to successfully guide management of cystic fibrosis in adult patients.
© RSNA, 2006
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LEARNING OBJECTIVES FOR TEST 1
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After reading this article and taking the test, the reader will be able to:- List the common abdominal manifestations of cystic fibrosis in the adult patient.
- Identify the imaging findings of the abdominal manifestations of cystic fibrosis.
- Describe the common and uncommon complications of cystic fibrosis seen in the abdomen in adult CF patients.
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Introduction
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Cystic fibrosis (CF) is the most common inherited fatal disease in whites, affecting approximately 1 in every 3500 children born yearly (1,2). Inheritance is autosomal recessive, and the gene mutations have been identified at a single locus on the long arm of chromosome 7 (1). The CF gene and its product, the CF transmembrane conductance regulator (CFTR), cause abnormal chloride ion transport on the apical surface of exocrine gland epithelial cells (3,4). This results in abnormally thickened, viscous secretions, which affect multiple organ systems. Mucous plugging, bronchiectasis, and recurrent infection are the well-known pulmonary manifestations, with respiratory failure the most common cause of mortality (5,6).
Owing to recent advances in the management of the respiratory and digestive components of CF, the median life expectancy is now over 30 years; it is projected that in today’s newborn infants, it will become more than 40 years (7). Identification of the CF gene and its product, CFTR, has widened awareness of the spectrum of the disease. It is now thought that varying phenotypic expressions of CF gene mutations can result in predisposition to disease in different organ systems (5,8).
As more CF patients are surviving into adulthood, extrapulmonary disease has become more commonplace. Forty percent of all CF patients are adults, and presenting complaints vary widely (2). A recent retrospective review has shown that 7% of CF patients do not present until adulthood, and only 39% of these patients have pulmonary symptoms as their sole complaint (9). In that study, 30% of the adults had normal radiographic studies of the chest (9). Abdominal complaints are common and nearly all organ systems are affected, including the hepatobiliary system, pancreas, and gastrointestinal tract and less commonly the kidneys. Of the patients in whom CF was diagnosed when they were adults, 26% presented with gastrointestinal symptoms at the time of initial assessment for CF and 4% had pancreatitis as the sole manifestation (9). Thus, it is important for the radiologist to be aware of the potential manifestations of CF below the diaphragm in order to provide accurate diagnoses and timely clinical guidance.
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Hepatobiliary Manifestations
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Liver disease is the second leading cause of death in patients with CF (3). Overall, it is estimated that 40% of CF patients develop liver disease, but only 1%–5% of these cases progress to portal hypertension and end-stage liver disease (5,10). The pathophysiology of liver disease in CF patients is unknown but is likely multifactorial. It has classically been attributed to abnormally thickened secretions that accumulate within bile ducts, slowing biliary flow and concentrating caustic bile components in the hepatic tissues (3,5,11). Hepatic enzyme analysis is known to have low sensitivity and specificity in the assessment of early CF-associated hepatic disease (12), and biopsy can be unreliable due to sampling error in focal disease processes (13,14).
Fatty infiltration of the liver has been reported in 30% of all CF patients on the basis of biopsy results, in 30%–50% on the basis of ultrasonographic (US) or computed tomographic (CT) criteria, and in 60% at autopsy (4,5,13,15) (Fig 1). It is rarely symptomatic unless associated with palpable hepatomegaly (16). The CT and US appearances of steatosis are well known. In one study, only 25% of diffusely hyperechoic livers in CF patients were fatty according to CT criteria (13). T1-weighted magnetic resonance (MR) images obtained with and without fat suppression can also depict fatty change (14). The cause of steatosis in CF patients is unknown, and there has been no proven relationship between steatosis and the subsequent development of focal biliary fibrosis or cirrhosis (1,13).
Biliary abnormalities range from cholelithiasis and sludge to ductal strictures and sclerosing cholangitis. A common abnormality is the microgallbladder, which has been found in up to 30% of CF patients in autopsy series (13,17). It is likely related to inspissated mucus and/or an inflammatory response resulting in atresia or stenosis of the cystic duct (14). Most patients are asymptomatic and require no further work-up (13,18). Cholelithiasis occurs in 12%–24% of patients with CF (5) (Fig 2). Sludge and mucus can fill the gallbladder lumen and result in false-positive results at hepatobiliary scintigraphy (5,14). Gallbladder wall thickening is nonspecific, especially in the setting of cirrhosis, ascites, hypoalbuminemia, and nutritional deficiencies.
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Figure 2. Cholelithiasis with gallbladder wall thickening in a 29-year-old man with CF. Oblique US image of the right upper quadrant shows multiple shadowing calculi (arrow) and mild diffuse thickening of the gallbladder wall (arrowhead).
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Intra- and extrahepatic bile duct abnormalities include strictures, beading, dilatation, and ductal calculi, all of which are similar to sclerosing cholangitis (14) (Fig 3). Abscesses can occur (Fig 4). CT and US can be insensitive in the evaluation of the ducts, and clinically suspected biliary abnormalities should be evaluated with endoscopic, percutaneous, or MR cholangiography (13). Intrahepatic ductal abnormalities have been found at MR cholangiography in 100% of CF patients with known liver disease and in 50% of CF patients without known liver disease (13,19). MR cholangiography is useful for better characterizing ductal abnormalities in CF patients with known liver disease and is more accurate for the diagnosis of ductal abnormalities in patients with clinically and sonographically occult liver disease (20).
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Figure 3a. Bile duct abnormalities in a 20-year-old man with CF. (a) Endoscopic retrograde cholangiopancreatogram shows strictures (white arrowhead) and dilatation (black arrowhead) of the bile ducts. Multiple filling defects (arrows) are also noted. (b) Oblique US image of the right upper quadrant shows multiple shadowing calculi (arrows) in the intrahepatic bile ducts.
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Figure 3b. Bile duct abnormalities in a 20-year-old man with CF. (a) Endoscopic retrograde cholangiopancreatogram shows strictures (white arrowhead) and dilatation (black arrowhead) of the bile ducts. Multiple filling defects (arrows) are also noted. (b) Oblique US image of the right upper quadrant shows multiple shadowing calculi (arrows) in the intrahepatic bile ducts.
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Figure 4a. Hepatic abscess in a 20-year-old man with CF (same patient as in Fig 3). CT was performed at a later date for evaluation of right upper quadrant pain. (a) Axial contrast-enhanced CT image shows a focal, round, hypoattenuating lesion with an enhancing rim (arrow) in the anterior segment of the right hepatic lobe, an appearance consistent with an abscess. (b) CT image obtained more inferiorly shows dilatation of an intrahepatic bile duct (arrow) in the left lobe.
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Figure 4b. Hepatic abscess in a 20-year-old man with CF (same patient as in Fig 3). CT was performed at a later date for evaluation of right upper quadrant pain. (a) Axial contrast-enhanced CT image shows a focal, round, hypoattenuating lesion with an enhancing rim (arrow) in the anterior segment of the right hepatic lobe, an appearance consistent with an abscess. (b) CT image obtained more inferiorly shows dilatation of an intrahepatic bile duct (arrow) in the left lobe.
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Focal biliary fibrosis is considered a characteristic histopathologic lesion in CF and has been estimated to be present in 78% of patients older than 24 years (13,21,22). It is postulated to be related to thick secretions and/or an inflammatory response within the intrahepatic bile ducts resulting in periductal thickening and fibrosis (5,13). The classic sonographic appearance is hyperechoic periportal thickening due to fibrosis or focal fat, with diffuse increased hepatic echogenicity (5,13) (Fig 5). Correlation of US findings with MR imaging findings showed that periportal echogenicity more frequently corresponds to fatty signal rather than fibrosis (14).
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Figure 5. Biliary fibrosis in a 20-year-old man with CF. Transverse US image of the right upper quadrant shows diffusely increased hepatic echogenicity with periportal increased echogenicity (arrows).
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The incidence of progression from focal biliary fibrosis to multinodular cirrhosis is unknown. Cirrhosis is estimated to occur in 5%–15% of CF patients (3), and progression to portal hypertension occurs in 1%–8% (3,11). Imaging findings are similar to those in other adult patients with cirrhosis and include a small, nodular, heterogeneous liver with portal hypertension, varices, and ascites (Fig 6). MR imaging findings include regenerative nodules and generalized fibrosis, which is best seen on axial T1-weighted fat-saturated images (14). The development of hepatocellular carcinoma is unusual, with only one reported case in a 32-year-old woman who had known CF-related liver disease since childhood and cirrhosis for at least 10 years (23).
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Figure 6a. Multinodular cirrhosis in a 21-year-old man with CF who had cirrhosis. The patient’s spleen was surgically removed due to complications of portal hypertension. (a, b) Axial T1-weighted spin-echo (a) and T2-weighted fat-suppressed fast spin-echo (b) MR images show a nodular liver (arrows). There is a small amount of perihepatic ascites on the T2-weighted image (arrowhead in b). (c) Axial contrast-enhanced CT image shows multiple small varices in the omentum (arrows) and surrounding the stomach (white arrowhead). Note the fatty replacement of the pancreas (black arrowhead).
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Figure 6b. Multinodular cirrhosis in a 21-year-old man with CF who had cirrhosis. The patient’s spleen was surgically removed due to complications of portal hypertension. (a, b) Axial T1-weighted spin-echo (a) and T2-weighted fat-suppressed fast spin-echo (b) MR images show a nodular liver (arrows). There is a small amount of perihepatic ascites on the T2-weighted image (arrowhead in b). (c) Axial contrast-enhanced CT image shows multiple small varices in the omentum (arrows) and surrounding the stomach (white arrowhead). Note the fatty replacement of the pancreas (black arrowhead).
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Figure 6c. Multinodular cirrhosis in a 21-year-old man with CF who had cirrhosis. The patient’s spleen was surgically removed due to complications of portal hypertension. (a, b) Axial T1-weighted spin-echo (a) and T2-weighted fat-suppressed fast spin-echo (b) MR images show a nodular liver (arrows). There is a small amount of perihepatic ascites on the T2-weighted image (arrowhead in b). (c) Axial contrast-enhanced CT image shows multiple small varices in the omentum (arrows) and surrounding the stomach (white arrowhead). Note the fatty replacement of the pancreas (black arrowhead).
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Pancreatic Manifestations
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Exocrine gland insufficiency affects 85%–90% of all CF patients and is a result of inspissated secretions leading to proximal duct obstruction (4,5,14) with subsequent acinar disruption and replacement by fibrous tissue and fat (1). Patients with CF diagnosed in adulthood are far more likely to be pancreatic enzyme sufficient than those with CF diagnosed in childhood (9). Those patients with residual pancreatic exocrine function are prone to recurrent episodes of acute pancreatitis (1,9,24) (Fig 7). Endocrine gland dysfunction is reported in 30%–50% and is thought to result from fibrosis and gland atrophy (4,5,9).
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Figure 7. Pancreatitis in a pancreatic sufficient 19-year-old woman with CF. Axial contrast-enhanced CT image shows enlargement of the pancreas with peripancreatic inflammation (arrows). There is also fatty infiltration of the liver (arrowhead).
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Complete fatty replacement is the most common pancreatic finding at imaging in adult CF patients (Fig 8), and the mean age of fatty replacement is 17 years (14). Sonographic findings include hyperechoic and atrophic pancreatic parenchyma. At MR imaging, the degree of fatty replacement will vary, with increased signal intensity on T1-weighted images reflecting fatty change and intermixed low signal intensity on T1-weighted images representing fibrosis (5,14). A gland that is markedly enlarged with fatty replacement has been termed lipomatous pseudohypertrophy of the pancreas by some authors (14,25,26) (Fig 9).
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Figure 8a. Complete fatty replacement of the pancreas. (a, b) Axial contrast-enhanced CT images, obtained at the levels of the pancreatic tail (a) and pancreatic head (b) in a 32-year-old man with CF, show replacement of the pancreatic parenchyma by fat (arrows). Splenomegaly is also present. (c) Axial T1-weighted MR image obtained in a 21-year-old man with CF shows similar findings (arrows).
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Figure 8b. Complete fatty replacement of the pancreas. (a, b) Axial contrast-enhanced CT images, obtained at the levels of the pancreatic tail (a) and pancreatic head (b) in a 32-year-old man with CF, show replacement of the pancreatic parenchyma by fat (arrows). Splenomegaly is also present. (c) Axial T1-weighted MR image obtained in a 21-year-old man with CF shows similar findings (arrows).
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Figure 8c. Complete fatty replacement of the pancreas. (a, b) Axial contrast-enhanced CT images, obtained at the levels of the pancreatic tail (a) and pancreatic head (b) in a 32-year-old man with CF, show replacement of the pancreatic parenchyma by fat (arrows). Splenomegaly is also present. (c) Axial T1-weighted MR image obtained in a 21-year-old man with CF shows similar findings (arrows).
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Figure 9a. Lipomatous pseudohypertrophy of the pancreas in a 49-year-old woman with CF. Axial contrast-enhanced CT images obtained at the levels of the pancreatic tail (a) and pancreatic head (b) show an enlarged pancreas with fatty replacement (arrows). The patient also has peritoneal carcinomatosis secondary to colon carcinoma. There is a serosal implant along the liver (black arrowhead) and omental infiltration (white arrowhead).
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Figure 9b. Lipomatous pseudohypertrophy of the pancreas in a 49-year-old woman with CF. Axial contrast-enhanced CT images obtained at the levels of the pancreatic tail (a) and pancreatic head (b) show an enlarged pancreas with fatty replacement (arrows). The patient also has peritoneal carcinomatosis secondary to colon carcinoma. There is a serosal implant along the liver (black arrowhead) and omental infiltration (white arrowhead).
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Pancreatic calcifications occur in roughly 7% of patients (21). They are usually found along the course of pancreatic ducts, are variable in both size and shape, and are often difficult to detect with MR imaging (14).
Pancreatic cysts are relatively common in CF patients, are usually small, measuring 1–3 mm (5,27), and are best demonstrated with T2-weighted MR imaging or MR cholangiopancreatography (14). Occasionally, aggregates of true epithelium-lined cysts completely replace the pancreas, a condition referred to as pancreatic cystosis (5,25) (Fig 10). It is thought to occur when the functional secretory capacity of the gland is maintained in the presence of ductal obstruction (27). Pancreatic cystosis is well demonstrated with US, CT, and MR imaging, and the imaging appearance can be similar to those of cystic pancreatic neoplasms, von Hippel–Lindau disease, and autosomal dominant polycystic kidney disease (25,27,28).
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Figure 10. Pancreatic cystosis in a 16-year-old girl with CF. Axial T2-weighted single-shot fast spin-echo MR image shows complete replacement of the pancreatic parenchyma by innumerable cysts (arrows).
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Abnormalities of the pancreatic duct are also encountered in CF patients and include strictures, beading, dilatation, and frank obstruction. Since most adult CF patients have an atrophic gland with fatty replacement, duct abnormalities can be difficult to demonstrate at imaging. The pancreatic duct is poorly demonstrated with US in CF patients (29) and is best demonstrated with MR cholangiopancreatography or endoscopic retrograde cholangiopancreatography (14).
Pancreatic carcinoma, although uncommon in CF patients, is one of the digestive tract malignancies for which CF patients are at increased risk (30).
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Gastrointestinal Manifestations
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Nearly the entire digestive tract is affected in patients with CF. Presenting complaints in adults with CF vary widely and are largely related to pancreatic exocrine deficiency, abnormal secretions, and their treatment.
Gastroesophageal reflux is seen in up to 27% of CF patients younger than 5 years (5,15,24). It is thought to be due to elevated abdominal pressures from chronic cough, hyperinflation, and diaphragm depression and to long-term use of medications that tend to reduce lower esophageal sphincter pressures (5). Complications related to chronic reflux disease, namely, esophagitis, strictures, and the development of Barrett metaplasia, can be seen in the adult. Although esophagitis, strictures, and esophageal carcinoma (Fig 11) can be detected at barium fluoroscopy or CT, the standard of reference is esophagogastroduodenoscopy, which is especially important in the surveillance of CF patients once Barrett metaplasia develops.
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Figure 11. Distal esophageal adenocarcinoma in a 26-year-old man with CF and a history of chronic esophageal reflux and Barrett esophagus. Barium esophagogram shows a distal malignant stricture (arrowhead).
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An increased frequency of peptic ulceration of the gastric and duodenal mucosa has been reported (5,24), likely related to impaired bicarbonate secretion and unbuffered gastric acid. Fluoroscopic findings are often masked by underlying mucosal abnormalities (5), including markedly thickened and distorted mucosal folds, nodular filling defects, mucosal smudging, and dilatation (5). An increase in the frequency of celiac sprue and giardiasis has also been noted (24), thus confounding the findings at barium examination and widening the differential diagnosis in these patients.
Distal intestinal obstruction syndrome or meconium ileus equivalent is a well-known complication and is thought to be caused by pancreatic insufficiency, thickened intestinal secretions, undigested food remnants, poor motility, and fecal stasis (5) with resultant impaction of mucofeculent material in the distal ileum and right colon (31). A similar phenomenon is described in the distal colon and rectum and can lead to chronic constipation and acquired megacolon (24). Distal intestinal obstruction syndrome occurs in 10%–24% of CF patients but has been reported to have decreased in frequency after the introduction of microsphere pancreatic enzymes (5,31,32). It has been reported as the most common gastrointestinal complication in CF patients following lung transplantation (31). The most common radiographic finding is a bubbly soft-tissue mass in the right lower quadrant. A water-soluble contrast enema can demonstrate the level of the obstruction and possibly reduce it (5). Clinical signs, symptoms, and plain radiographic findings can be somewhat nonspecific; in such cases, CT allows one to pinpoint the diagnosis (Fig 12). Surgical intervention may be necessary.
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Figure 12a. Distal intestinal obstruction syndrome in a 37-year-old man with CF. (a) Scout radiograph for abdominal CT shows a nearly gasless abdomen. Bronchiectasis is present at the lung bases. (b, c) Axial contrast-enhanced CT images show dilated proximal small bowel loops (arrows in b) leading to a mid–small bowel loop with bubbly intraluminal contents (arrowhead in c). A small amount of ascites and mild edema of the small bowel mesentery are present. This case is located somewhat more proximally than is usually seen. The patient was treated with conservative medical management with resolution of the symptoms and radiologic findings.
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Figure 12b. Distal intestinal obstruction syndrome in a 37-year-old man with CF. (a) Scout radiograph for abdominal CT shows a nearly gasless abdomen. Bronchiectasis is present at the lung bases. (b, c) Axial contrast-enhanced CT images show dilated proximal small bowel loops (arrows in b) leading to a mid–small bowel loop with bubbly intraluminal contents (arrowhead in c). A small amount of ascites and mild edema of the small bowel mesentery are present. This case is located somewhat more proximally than is usually seen. The patient was treated with conservative medical management with resolution of the symptoms and radiologic findings.
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Figure 12c. Distal intestinal obstruction syndrome in a 37-year-old man with CF. (a) Scout radiograph for abdominal CT shows a nearly gasless abdomen. Bronchiectasis is present at the lung bases. (b, c) Axial contrast-enhanced CT images show dilated proximal small bowel loops (arrows in b) leading to a mid–small bowel loop with bubbly intraluminal contents (arrowhead in c). A small amount of ascites and mild edema of the small bowel mesentery are present. This case is located somewhat more proximally than is usually seen. The patient was treated with conservative medical management with resolution of the symptoms and radiologic findings.
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Another cause of right lower quadrant pain is intussusception. It affects approximately 1% of patients but occurs most commonly in older patients and is found in nearly 20% of those CF patients presenting with obstruction (5,32). It is most frequently ileocolic and is related to an inspissated fecal mass that acts as a lead point. It may occur as a complication of distal intestinal obstruction syndrome (32). Radiologic appearances of intussusception range from a doughnut or pseudokidney appearance at US to the target sign of edematous bowel and intermixed mesenteric fat at CT (5) (Fig 13). Although a water-soluble contrast enema may allow successful reduction, recurrence rates are high.
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Figure 13. Ileo-ileal intussusception in a 29-year-old man with CF. Axial contrast-enhanced CT image shows the intussusceptum (arrow) outlined by oral contrast material within the intussuscipiens (arrowhead).
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Acute appendicitis is somewhat unusual and is reported to occur in only 1%–4% of patients (24,32) (Fig 14), despite the fact that the appendiceal lumen is often swollen and filled with inspissated secretions at autopsy (32). Chronic appendicitis and pain from chronic appendiceal distention have been described (24). Differentiating acute appendicitis from a chronically distended appendix with imaging alone is difficult if not impossible.
The colon is also often abnormal in patients with CF. Proximal colonic wall thickening, pericolonic fat proliferation, and mesenteric fat infiltration have all been reported (33,34). Postulated causes include chronic inflammation and edema from persistent thickened secretions and bowel stasis.
Fibrosing colonopathy is a known cause of colonic stricture and obstruction and typically involves the right colon. It is thought to be related to high-strength pancreatic enzyme replacement (5) and is almost exclusively reported in children. It is thought to no longer be a clinical problem with the increase in awareness and decrease in enzyme dosing (2) (John Lloyd-Still, MD, written communication).
Pneumatosis intestinalis is usually confined to the colon in patients with CF and often coincides with the development of obstructive lung disease (5,35). It is thought to result from the dissection of air from the pulmonary interstitium to the perivascular connective tissue planes below the diaphragm (5,35). Although it is most often clinically silent (35), it results in a broad differential diagnosis and subsequent surgical consultation in CF patients presenting with abdominal pain. The CT findings are classic and include cystic submucosal and subserosal foci of air attenuation that line up along the dependent portion of the bowel wall.
Rectal mucosal prolapse, reported in up to 20% of patients with CF, is usually found in younger patients in whom CF has not yet been diagnosed (5,24) and is related to frequent bulky stools and diminished muscle tone (5). Adult patients with CF are usually not affected (5,24) unless they are noncompliant with or unable to tolerate pancreatic supplementation.
Gastrointestinal malignancies are now more commonly reported as CF patients live into adulthood (30), and the diagnosis is often delayed. For CF patients aged 20–29 years, the odds ratio is 20:1 for gastrointestinal malignancy (30,32,36). Nine of 24 reported gastrointestinal malignancies have been colon carcinoma (32). Causes are unclear but may be related to differential expressions of the CFTR gene or chronic pathologic changes to the colonic mucosa (36). Nevertheless, the colon must be carefully scrutinized at barium studies and CT in adult patients with CF (Fig 15).
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Figure 15. Adenocarcinoma of the right colon in a 42-year-old man with CF. Axial nonenhanced CT image, obtained after administration of oral contrast material only, shows an annular mass (arrowhead) in the ascending colon.
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Another complication of CF is pseudomembranous colitis (Fig 16). Nearly 50% of CF patients are carriers of Clostridium difficile, and the frequent use of antibiotics puts them at significant risk (32). However, C difficile colitis in CF patients is rare, and it is thought that the CFTR-mediated chloride channel is unresponsive to the toxin in the colon (32).
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Figure 16a. Pseudomembranous colitis in a 24-year-old woman with CF. Scout radiograph (a) and axial contrast-enhanced CT image (b) show diffuse mural thickening of the colon (arrows). Bronchiectasis is also present at the lung bases on the scout radiograph.
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Figure 16b. Pseudomembranous colitis in a 24-year-old woman with CF. Scout radiograph (a) and axial contrast-enhanced CT image (b) show diffuse mural thickening of the colon (arrows). Bronchiectasis is also present at the lung bases on the scout radiograph.
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Renal Manifestations
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Renal disease is not a common complication of CF. The most prevalent entity is nephrolithiasis (Fig 17), which is estimated to occur in 3.0%–6.0% of CF patients in comparison to 1%–2% of age-matched control subjects without CF (37). The exact mechanism of stone disease is unclear. However, the CFTR protein is expressed in abundance in the kidney, and abnormal gene expression may result in subtle alterations in the concentrating and diluting of urine, resulting in nephrocalcinosis and/or urolithiasis (38). Stones are usually composed of calcium oxalate, and patients are often found to have hyperoxaluria, decreased levels of urinary citrate, and depressed urinary volumes (39,40). The long-term use of antibiotics resulting in the absence of Oxalobacter formigenes, a normal enteric flora that assists in degrading oxalate, is also thought to play a role in stone formation (37).
CFTR protein expression may also provide a hypothesis for differences in the renal handling of some potentially nephrotoxic drugs that are used in the management of CF (38). Furthermore, as the prognosis improves for patients with CF, secondary renal complications, such as interstitial nephritis due to antibiotic therapy (1) and amyloidosis, are likely to become more prevalent (38).
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Conclusions
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Recent advances in the clinical management of CF have had a significant impact on patients’ life expectancy. Hepatobiliary, pancreatic, and gastrointestinal complications of the disease increase in prevalence as the patient ages. Recognition of the wide variety of pathologic conditions seen below the diaphragm at imaging is important to successfully guide management.
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Footnotes
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Abbreviations: CF = cystic fibrosis, CFTR = CF transmembrane conductance regulator
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References
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Abstract
LEARNING OBJECTIVES FOR TEST...
