Sunday, January 24, 2010

Disseminated tuberculosis - CT

Disseminated tuberculosis (TB) is a contagious bacterial infection that has spread from the lungs to other parts of the body through the blood or lymph system. The differential diagnosis of miliary nodules in bilateral lungs are tuberculosis, metastases, sarcoidosis, lymphoma, hypersensitivity pneumonitis and rare causes like silicosis, beryliosis, stanosis. Depending imaging findings and patients clinical deatils, one can differentiate each other.
The differential diagnosis of patients with fever, splenomegaly, and multiple hypoechoic hypoattenuating splenic lesions includes splenic abscesses that may be bacterial, fungal, or granulomatous in nature. Pyogenic abscesses are usually solitary. On US images, they appear as small irregular hypoechoic lesions that may evolve into a poorly defined heterogeneous mass. On CT images, they typically appear as single irregularly marginated hypoattenuating lesions. The presence of intralesional gas is pathognomonic of pyogenic infection, although it occurs infrequently. Multiple splenic abscesses, usually smaller than 2 cm in diameter, are commonly associated with nonbacterial infections (ie, fungal and granulomatous infections). Fungal abscesses, when visible, characteristically appear on US images as round hypoechoic lesions with a central hyperechoic area (ie, “bull's-eye” or “target” appearance) that corresponds to inflammatory cells with a surrounding hypoechoic band of fibrosis. The “wheel-in-a-wheel” pattern is seen when the central portion becomes necrotic and hypoechoic. Contrast-enhanced CT typically depicts fungal splenic abscesses as multiple small low-attenuation lesions. Patients with cat-scratch disease may also develop splenomegaly and splenic microabscesses. Neoplasms that involve the spleen—such as lymphoma (both Hodgkin and non-Hodgkin lymphoma), leukemia, metastasis, or even Langerhans cell histiocytosis—may manifest as focal hypoechoic hypoattenuating lesions. Sarcoidosis, which is a systemic granulomatous disease of unknown origin, may also have abdominal involvement with lymphadenopathy and hypoattenuating nodules in the liver and spleen. It is generally impossible to differentiate visceral TB lesions from fungal infections, lymphoma, or metastasis—unless they are associated with other typical abdominal TB findings, such as lymph node or bowel involvement.

Saturday, January 23, 2010

Oriental cholangitis - MRI

42 year old female came with history of recurrent attacks of abdominal pain, fever, and jaundice. MRCP coronal HASTE image of upper abdomen shows dilatation of intrahepatic biliary radicles and CBD with multiple calculi within the hepatic ducts (L>R) and CBD (arrows). No calculi in the gall bladder. Thick slab MRCP image (left) better shows the IHBR and CBD dilatation with hepaticolithiasis and choledocholithiasis. Incidentally note the right retrocaval ureter.

Recurrent pyogenic cholangitis (RPC) or Oriental cholangiohepatitis is a recurrent and chronic and biliary tract infectious process typically seen in the Asian population, particularly Chinese. The disease involves recurrent episodes of infectious cholangitis with fever, abdominal pain, and jaundice. The causative infectious agents are typically bacterial such as E. coli and other coliforms. However biliary tract parasites such as Ascaris lumbricoides and Clonorchis sinensis are common coexistent pathogens, and it is not clear which infectious agents are the primary cause or representative of secondary superinfection.
The recurrent infections lead to bile duct dilatation, strictures, obstruction, and calculi. The bile duct dilatation may be pronounced and involves both the intrahepatic and extrahepatic ducts. There is a predilection for ductal involvement in the left lobe of the liver but diffuse intrahepatic disease can be seen. The extrahepatic bile duct can be quite dilated up to as much as 3-4cm in diameter. The dilatation of the extrahepatic duct may be secondary to loss of elasticity of the duct wall due to chronic infection or it may be due to ampullary narrowing.
The calculi are typically bile pigment stones with varying amounts of calcium. The stones have a mud or paste-like consistency. The stones presumably form due to bacterial enzymes causing deconjugation of bilirubin which then precipitates as calcium bilirubinate. In addition it has been postulated that a low protein diet as is seen in some Asian populations may play a role in formation of intraductal stones. MRCP is gold standard non invasive investigation for diagnosis of oriental cholangitis.

Friday, January 15, 2010

Crohn's disease - CT Enteroclysis

24 year old female came with history of diarrhea and pain abdomen. CT enteroclysis shows significant concenteric wall thickening in the descending colon.

Crohn's disease (also known as Crohn-Lesniowski Disease, or "Charlotte Forditis" morbus Lesniowski-Crohn, granulomatous colitisand regional enteritis) is an inflammatory disease of the intestines that may affect any part of the gastrointestinal tract from anus to mouth, causing a wide variety of symptoms. It primarily causes abdominal pain, diarrhea (which may be bloody), vomiting, or weight loss, but may also cause complications outside of the gastrointestinal tract such as skin rashes, arthritis and inflammation of the eye.

The first investigation to be done in suspected case of chrons disease is barium study, Ba meal follow through and barium enema. Barium study shows bowel luminal narowing and proximal dilatation. Multiple areas of narrowing may be seen in the small and large bowel. Cross sectional imaging mainly CT and MRI (CT&MRI Enteroclysis) are done to analyze specifically for the presence and character of a pathologically altered bowel segment (wall thickness, pattern of attenuation, degree of enhancement, length of involvement), stenosis and prestenotic dilatation, skip lesions, fistulas, abscess, fibrofatty proliferation, increased vascularity of the vasa recta (comb sign), mesenteric adenopathy, and other extraintestinal disease involvement. The normal thickness of the wall of the small intestine and colon is 1–2 mm and 3 mm, respectively, when the lumen is distended. Any portion of the bowel wall that exceeds 4–5 mm is considered abnormal. Bowel wall thickening, usually ranging from 1–2 cm, is the most consistent feature of Crohn disease on cross-sectional images. Mural stratification (“target” or “double halo” appearance) is often seen in active lesions, particularly after the intravenous administration of contrast medium. An inflamed bowel wall demonstrates marked enhancement after intravenous contrast material injection, and the intensity of enhancement correlates with the degree of inflammatory lesion activity.

Saturday, January 9, 2010

Bronchocele - CT

Chest scanogram of 23 year old male patient came with history of cough showing eliptical ares of increased opacity seen in the right upper lobe, medial end pointing towards the hilum and the lesion is sharply marginated.
Contrast enhanced CT scan showing non enhancing fluid attenuating lesion seen in the right upper lobe appears to be with in the dilated bronchi of posterior segment of right upper lobe. Can better appreciate on coronal reformatted image.

Bronchocele is commonly seen in congenital bronchial atresia, where there will be fluid accumulation in the bronchus distal to the atretic segment of bronchus. There are other rare causes for bronchocele like tumor obstructing the segmental bronchus, commonly carcinoids. The distal involved alveoli may show hypoplasia or a probable consequence of decreased ventilation and perfusion. These alveoli however remain open by collateral air drift occurring by the interalveolar pores of Kohn (air drift) or the bronchoalveolar channels of Lambert or the interbronchiolar channels with some amount of air trapping. Although radiograph is the first investigation to be done and suspected on it. The findings may show as described above in our case. Spiral CT is the examination of choice, not only to show all the components of the anomaly and to estimate the extent of air trapping but also for ruling out differential diagnosis such as bronchogenic cyst, bronchiectasis, aspergillosis, completely thrombosed arteriovenous malformation or pulmonary aneurysms and tumors.

Tuesday, January 5, 2010

Annular Pancreas - Barium meal.

34 year old male patient came with recurrent pancreatits. Barium meal showing smooth narrowing in the second part of duodenum. Annular pancreas was confirmed on MRCP.

Annular pancreas is a rare congenital anomaly in which incomplete rotation of the ventral anlage leads to a segment of the pancreas encircling the second part of the duodenum. It has a prevalence of one in 2,000 persons and occurs either as an isolated finding or with other congenital abnormalities. There are two types of annular pancreas: the extramural type and the intramural type. In the extramural type, the ventral pancreatic duct encircles the duodenum to join the MPD. In the intramural type, the pancreatic tissue is intermingled with muscle fibers in the duodenal wall, and small ducts drain directly into the duodenum.

Annular pancreas can be diagnosed on the basis of CT and MR imaging findings that reveal pancreatic tissue and an annular duct encircling the descending duodenum. ERCP is useful in substantiating the diagnosis and defming the ductal anatomy. ERCP shows a normally located main duct in the pancreatic body and tail and encirclement of the duodenum by a small duct in the pancreatic head. In most cases (85%), the duct within the annular portion of the pancreas communicates with the main pancreatic duct.

Sunday, January 3, 2010

Primitive Neuroectodermal Tumor (PNET) of Skull vault : CT and MRI

4 year old female child came with history of mass in the right side of the head in parietal region. CT scan shows large heterogenously enhancing soft tissue mass lesion seen in both intra and extracranial regions, the intracranial component is extradural causing mass effect on the right cerebellar hemisphere. There is bone erosion of right parietal bone.

MRI of the same patient T2 WI showing similar findings with large extra and intracranial components. There is complete involvement of the right parietal bone. Biopsy proved to be PNET.

Primitive Neuroectodermal Tumor (PNET) is a soft tissue sarcoma classically described under small round blue cell tumors (SRBCT). Synonyms include : PNET, Peripheral neuroepithelioma, Peripheal neuroblastoma, Askin tumor (Thoracopulmonary PNET) and Extraosseous Ewing's sarcoma. The incidence is 1% of the sarcomas. They often (75%) occure in the age of less than 35 years. Most investigators now believe that Ewing's sarcoma and PNET are different morphological expressions of one tumor type. In general, Ewing's sarcoma arises within the bone while PNET arises within soft tissues. PNET arising from the dura or skull vault is very rare and in this case it is diffucult to predict the origin of the tumor.Radiograph is often the first investigation to be done. CT and MRI are the investigations of choice to see for the extent of the lesion. MRI is preferred over CT scan. These can be used to look for the response to chemo and radiotherapy.Here is the link to the PNET at various sites:

Search This Blog