Cystic Fibrosis

Published on 19/07/2015 by admin

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Last modified 22/04/2025

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 Complete fatty infiltration and replacement of parenchyma (often by end of teenage years)

image Pancreatic cysts: Usually small (< 3 mm), but can be larger and can completely replace pancreas (cystosis)
image Repeated episodes of acute pancreatitis with development of chronic pancreatitis
• Liver

image 30-50% develop hepatic steatosis ± hepatomegaly
image Can develop multinodular cirrhosis in severe cases
• Biliary

image Biliary abnormalities similar to primary sclerosing cholangitis (PSC)
image Gallstones ± gallbladder wall thickening and sludge
• Bowel

image Inspissated fecal material resulting in proximal obstruction, most often in infants (meconium ileus)
image Obstruction can also occur in adults: Distal intestinal obstruction syndrome (DIOS)
image Increased risk for intussusception
image Chronically distended appendix may be difficult to distinguish from acute appendicitis

– Appendicitis in 1-4% of patients

TOP DIFFERENTIAL DIAGNOSES

• Pancreatic lipomatous pseudohypertrophy
• Shwachman-Diamond syndrome
• Normal fatty lobulation
• Chronic pancreatitis
• Pancreatic cystic neoplasms (IPMN, mucinous cystic neoplasms, etc.)

CLINICAL ISSUES

• Overall prognosis for CF has dramatically improved, with average life expectancy now 35-40 years
• Respiratory failure most common cause of mortality, with liver disease 2nd leading cause of death
• Pancreatic insufficiency most common (∼ 85%) GI manifestation of CF
image
(Left) Axial CECT shows the classic lipomatous replacement and pseudohypertrophy of the pancreas image in a young adult patient with cystic fibrosis (CF).

image
(Right) Axial CECT in the same patient shows dilated proximal small bowel image and collapsed distal small bowel image. Just proximal to the point of transition is the classic “small bowel feces sign” image associated with mechanical small-bowel obstruction, with the obstruction caused by inspissated enteric contents (distal intestinal obstruction syndrome or DIOS).
image
(Left) Axial CECT demonstrates heterogeneous lipomatous replacement of the pancreatic parenchyma image but less pseudohypertrophy. This 29-year-old woman had longstanding pancreatic exocrine dysfunction due to CF.

image
(Right) Coronal CECT demonstrates simple-appearing cysts image in the pancreatic head in a young patient with CF. While pancreatic cysts are often very small in CF patients, they can rarely be larger, as in this case.

TERMINOLOGY

Abbreviations

• Cystic fibrosis (CF)

Synonyms

• Mucoviscidosis

Definitions

• Recessively inherited disorder of epithelial chloride transport caused by mutation of CF transmembrane conductance regulator (CFTR) gene

image Pulmonary manifestations are primary cause of morbidity and mortality
image CF increasingly seen to affect GI tract due to improved life expectancy

IMAGING

General Features

• Best diagnostic clue

image Diffuse fatty replacement of pancreas is most common abdominal imaging finding
• Location

image Most common sites of involvement are lungs, pancreas, bowel, liver, and exocrine glands

CT Findings

• Pancreatic manifestations

image Early childhood: Heterogeneous attenuation of pancreas
image Later childhood: Complete fatty replacement of parenchyma (often by teenage years)
image Pancreatic cysts: Usually simple in appearance

– Related to inspissated secretions which lead to ductal obstruction
– Cysts are usually small (< 3 mm), but can be larger
– Cysts may diffusely replace pancreas (cystosis)
– Usually occur in patients in their 20s, and may be symptomatic as result of cyst hemorrhage
image Repeated episodes of acute pancreatitis with development of chronic pancreatitis

– Pancreatic ductal strictures, dilatation, beading, etc.
image May have scattered calcifications (< 10% of patients)
image Increased risk of pancreatic cancer (very rare)

MR Findings

• Enlarged pancreas with diffuse fatty infiltration appears hyperintense on T1WI
• Pancreas can also appear abnormally hypointense on T1WI due to chronic pancreatitis and fibrosis
• Pancreatic cysts well demonstrated on T2WI and MRCP (hyperintense)
• Pancreatic duct abnormalities also occasionally seen

Ultrasonographic Findings

• Pancreas may be barely identifiable as result of diffuse fibrofatty replacement
• Macroscopic multiple cysts
• Hypoechoic enlargement of pancreas noted in some children with acute pancreatitis

Other Abdominal Findings

• Liver

image 30-50% develop hepatic steatosis ± hepatomegaly

– Can be visualized with US, CT, or chemical shift MR
– Fatty liver usually asymptomatic and does not correlate with development of CF-related cirrhosis
image Cirrhosis in 5-15% of all CF patients with portal hypertension in 1-8%
image Multinodular cirrhosis in severe cases

– Volume loss, wide fissures, fibrosis, regenerative nodules, ± signs of portal hypertension
• Biliary

image Gallstones in up to 1/4 of patients with CF, often with nonspecific gallbladder wall thickening and sludge
image Microgallbladder in 30% of CF patients at autopsy

– Probably due to chronic stenosis or atresia of cystic duct (does not usually cause symptoms)
image May develop bile duct abnormalities very similar to primary sclerosing cholangitis (PSC), including strictures, bile duct wall thickening, biliary obstruction, etc.

– May develop focal biliary fibrosis (> 3/4 of patients with CF older than 24 years)

image Periductal thickening and fibrosis due to thick secretions within duct and reactive inflammation
image Focal thickening of bile duct with changes in adjacent liver parenchymal density/signal
image US: Hyperechoic periportal thickening and diffuse hepatic hyperechogenicity
– MRCP best noninvasive modality for identifying changes
• Esophagus

image Gastroesophageal (GE) reflux seen in 27% of patients younger than 5 years and increases with age
image Complications detected with esophagram or endoscopy
• Bowel

image ↑ frequency of peptic ulcer disease (gastric or duodenal)
image Obstruction

– Bubbly fecal mass within bowel causing proximal obstruction, most often in infants (meconium ileus)
– Obstruction can also occur in adults: Distal intestinal obstruction syndrome (DIOS) (previously known as meconium ileus equivalent)

image Obstruction results from thickened intestinal secretions, poor motility, and formation of mass-like fecal material which obstructs bowel
image Usually obstructs at distal ileum or right colon (rarely at distal rectum)
image Water-soluble contrast enema might be able to reduce obstruction
image Increased risk for intussusception

– More common in older patients
– Most often ileocolic intussusception, usually due to inspissated fecal material acting as lead point
– US: “Doughnut” or pseudokidney appearance
– CT: “Target” sign of edematous bowel and intermixed mesenteric fat
– Water-soluble contrast enema can be used for reduction, but high rates of recurrence
image Chronically distended appendix common with internal inspissated high-density material

– Differentiating acute appendicitis from chronic distention is difficult with imaging
– Appendicitis in 1-4% of patients
image Abnormalities of colon can include proximal colonic wall thickening, proliferation of fat surrounding the colon, and pericolonic fat stranding

– Benign pneumatosis due to air dissecting below diaphragm into bowel wall due to lung disease
– Increased susceptibility to pseudomembranous colitis
– Increased risk of colon cancer
– Rectal mucosal prolapse usually in younger patients

image 20% of patients with CF
• Renal

image Nephrolithiasis in 3-6% CF patients
image Interstitial nephritis due to antibiotics and amyloidosis will likely become more common as patients live longer

DIFFERENTIAL DIAGNOSIS

Pancreatic Lipomatous Pseudohypertrophy

• Diffuse enlargement and fatty replacement of pancreas
• Associated with chronic liver disease; no signs of CF

Shwachman-Diamond Syndrome

• Pancreatic lipomatosis associated with short stature
• Appearance of pancreas is identical to CF

Normal Fatty Lobulation

• Fatty replacement of pancreatic parenchyma with mild glandular atrophy
• Common in elderly, obese, and diabetic patients

Chronic Pancreatitis

• Pancreatic atrophy, parenchymal and ductal calcifications, and pancreatic ductal beading, irregularity, and dilatation
• Pancreatic volume is usually decreased

image May have focal soft tissue density enlargement (usually in head)
• Intra- or peripancreatic cysts
• Pancreatic findings may mimic CF, but lacks other clinical signs

Pancreatic Cystic Neoplasms (IPMN, etc.)

• May be indistinguishable from CF-related pancreatic cysts without clinical history

PATHOLOGY

General Features

• Etiology

image Mutations of CFTR gene lead to multisystem pathology
image Disruption of chloride ion, bicarbonate, and water transport in duct cells
image Primary ductal cell chloride channel abnormality results in dehydrated protein-rich secretions obstructing proximal ducts

– Leads to acinar cell destruction, fibrosis, and exocrine insufficiency
– Also causes ductal obstruction leading to lung infections, biliary obstruction, etc.
• Genetics

image Mutations in CFTR gene
image Autosomal recessive gene on chromosome 7

Lab

• Positive sweat test
• Genotyping has proved useful in identifying gene carriers; antenatal diagnosis and treatment

CLINICAL ISSUES

Presentation

• Clinical profile

image Usually diagnosed in infants with meconium ileus, lung infections, etc.

– Until recently, patients died in childhood of pulmonary infections and respiratory failure
– Longer survival now reveals other multisystem manifestations of cystic fibrosis
image 7% of CF patients do not present until adulthood

– Of these, 26% present with GI symptoms and 4% with pancreatitis
image Chronic pulmonary disease (infections, bronchiectasis)
image Symptoms of pancreatic dysfunction

– Steatorrhea, malabsorption, fat intolerance

image Pancreatic insufficiency usually present from birth
– Repetitive acute pancreatitis leading to chronic pancreatitis

image Susceptible to infection by Staphylococcus aureus and Pseudomonas aeruginosa
image Pancreatitis in 10% of CF patients
– Endocrine (diabetes) and exocrine dysfunction
image Symptoms of hepatobiliary dysfunction

– Inspissated secretions obstruct bile ducts and caustic bile acts on adjacent parenchyma
– Liver disease can vary from asymptomatic elevation in liver function tests to end-stage liver disease and cirrhosis
– 10-20% of patients develop chronic liver disease (including cirrhosis and portal hypertension)
– Cholelithiasis in 10% of patients
image Intestinal manifestations

– Intestinal obstruction

image Usually in infancy (meconium ileus), but may occur in adults as well (DIOS or meconium ileus equivalent)
– Intussusceptions (1% of patients)
image Infertility in males (azoospermia, turbid semen)

Demographics

• Age

image Children most affected
image Patients reaching adulthood represent rapidly growing percentage of CF population
• Ethnicity

image More common in Caucasians

– Most common inherited fatal disease in Caucasians
• Epidemiology

image CF prevalence: 1 in 3,500
image 85–90% of CF patients have pancreatic exocrine gland insufficiency

– Cystic fibrosis is major cause of pancreatic exocrine failure in childhood
image 30-50% of CF patients have pancreatic endocrine gland dysfunction

Natural History & Prognosis

• Overall prognosis for CF has dramatically improved due to screening and better treatment, with average life expectancy now 35-40 years
• Respiratory failure most common cause of mortality

image Liver disease is 2nd leading cause of death

– Liver disease increasingly being seen as CF life expectancy increases
• Pancreatic insufficiency most common (∼ 85%) GI manifestation of CF

image Varies depending on degree of ductal obstruction by mucus, which leads to exocrine gland atrophy, progressive fibrosis, and cyst formation
image CF may predispose to pancreatic cancer

Treatment

• Aggressive nutritional and pancreatic enzyme therapy
• DIOS usually treatable with hydration, laxatives, or water soluble contrast enema although severe cases may require surgery

image
(Left) Axial CT image shows diffuse pneumatosis image of the transverse and left colon. The patient was completely asymptomatic, and this was felt to be benign pneumatosis due to gas dissecting from the chest into the bowel wall as a result of the patient’s lung disease.
image
(Right) Axial NECT in a 24-year-old woman with CF shows an unusually severe degree of pancreatic calcification image. Scattered, small calcifications are a more common finding in this disease.
image
(Left) Axial T2WI in a 16-year-old girl with CF demonstrates complete fatty replacement image of the body and tail of the pancreas. Note that the pancreas consequently shows high T1WI signal.

image
(Right) Coronal MRCP in the same patient shows a septate cystic mass in the pancreatic head image that mimics a cystic neoplasm. However, pancreatic cysts of variable size are commonly encountered in patients with CF.
image
(Left) Axial CECT in a 31-year-old man shows classic cystic bronchiectasis in the lungs. Many patients are being kept alive longer with better medical care and even lung transplantation, resulting in an increased prevalence of extrapulmonary manifestations of CF.

image
(Right) Axial CECT in the same patient shows that the liver is small and cirrhotic with obvious signs of portal hypertension, including splenomegaly and large varices image. The pancreas shows fatty replacement image.
image
Axial NECT shows lipomatous replacement of the entire pancreas.

image
Axial NECT shows lipomatous replacement and pseudohypertrophy of entire pancreas.
image
Axial NECT shows hyperaeration of the upper lobes with cystic bronchiectasis in a patient with CF.
image
Axial CECT shows lipomatous replacement of the pancreas and 1 of several small cysts image.
image
Coronal CECT demonstrates a simple-appearing cyst image in the pancreatic tail in a young patient with CF. Notice the fatty infiltration of the surrounding pancreatic tail. While pancreatic cysts are often very small in CF patients, they can rarely be larger, as in this case.
image
Axial CT image demonstrates diffuse pneumatosis in the rectum. The patient was completely asymptomatic, and this was felt to be benign pneumatosis due to gas dissecting from the chest into the bowel wall as a result of the patient’s lung disease.
image
Axial CECT in a young adult with cystic fibrosis shows a moderate degree of lipomatous pseudohypertrophy of the pancreas image. The pancreatic duct is of normal caliber image.

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