Septic arthritis of hip joint

 Young male patient with fever of ~5-6 weeks duration, right hip pain.

STIR Coronal : Green arrow - joint effusion, Orange arrow: asymmetric red marrow / marrow edema.
(See last MRI image also)

STIR Axial image, Grade 3 joint effusion

STIR Axial image, marked.

Thickening and enhancement of the joint capsule / synovial layers.

Ultrasound: Echogenic fluid with debris within the anterior synovial recess. Anterior peri-articular muscle edema+. Probe tenderness+.

Eventhough the T1 hypointense signals in the intertrochanteric region (left) can be explained by the presence of residual red marrow in this 20yr old patient, the signal intensity is markedly reduced on right side, suspicious of marrow edema.

UR- Quiz 1 - (4th June 2018) : What's your diagnosis?

 69y Female. History of  transient loss of consciousness and fall resulting in side of head hitting a window, 2 years back, with slowly progressing swelling in left side of head.

ANSWER HERE...

Ring shaped lateral meniscus

Ring shaped lateral meniscus is a very rare anatomical variant which can easily mimic and make it difficult to distinguish from a bucket handle tear. Unlike the normal C-shape, this variant forms a complete ring.

Usually the lateral portion appears as in normal cases, with angular margins or sometimes can appear deficient anteriorly. The additional medial component appear like displaced torn fragment and easily gets mistaken for a bucket handle tear (where the body of meniscus will be truncated c.f. ring meniscus).

In differentiation from central perforation of a discoid lateral meniscus, the inner margins in central perforation will be irregular with degenerative changes. Associated osteophytes and chondral lesions may also be seen unlike a case of ring shaped lateral meniscus.

Pancreatic pseudocyst with duct communication (CT)

Pancreatic pseudocysts are the most common (85% to 90%) cystic lesions of pancreas, which are encapsulated peripancreatic or remote fluid collections developing after 4 weeks of an episode of acute pancreatitis. These are called pseudocysts as cyst lining is formed of fibrous tissue and not true epithelium. Cyst contents are rich in amylase.

Causes of pancreatic pseudocysts include Acute or chronic pancreatitis (most common), pancreatic trauma and rarely iatrogenic (e.g. partial gastrectomy). In cases of acute pancreatitis with inflammatory changes and seeing fluid collection developing wall or capsule in the peri-pancreatic region in follow-up imaging, is usually diagnostic of a pseudocyst. These usually arise 4 to 6 weeks after an acute episode. Pseudocysts can be followed up if the patient is asymptomatic or the cyst is smaller than 6cm as there is a chance of spontaneous resolution in smaller cysts.¹

Complications include secondary infection, hemorrhage, rupture and mass effect on adjacent structures.¹

Above axial images of contrast CT shows a large, peripherally enhancing cystic area (green arrow) in relation to the pancreas, consistent with a pseudocyst. Yellow arrow points to the pancreatic head head and orange arrow points to the distal CBD.

 

Green arrows mark the pancreatic pseuocyst and blue arrow points to the stretched residual pancreatic parenchyma of body region.


 

Sagittal reformats showing the duct (yellow arrows) in tail region.

Sagittal MPR and Sagittal Minimum Intensity Projection, showing the PD and the pseudocyst.

A communication between the PD and the pseudocyst is demonstated in the above image. 

Cysts communicating with PD are difficult to treat and tend to recur.

Presence of internal dependent debris level is regarded as highly specific for the diagnosis of pancreatic pseudocysts in MRI ².




References:
1. Imaging Diagnosis of Cystic Pancreatic Lesions: Pseudocyst versus Nonpseudocyst
Young H. Kim, Sanjay Saini, Dushant Sahani, Peter F. Hahn, Peter R. Mueller, Yong H. Auh
Radiographics, May 2005.

2. Differentiating Pancreatic Cystic Neoplasms from Pancreatic Pseudocysts at MR Imaging: Value of Perceived Internal Debris.
Michael Macari, Myra E. Finn, Genevieve L. Bennett, Kyunghee C. Cho,
Elliot Newman, Cristina H. Hajdu, James S. Babb.
Radiology April 2009.

3. Radiopaedia.

Plain CT Brain findings in an adolescent patient with Tuberous Sclerosis

Tuberous Sclerosis (TS) or Bournville disease is a rare Autosomal Dominant (AD) neurocutaneous syndrome (phakomatoses) characterized by development of multiple benign tumors of in various organs. Since the characteristic clinical triad mentioned is mental retardation, adenoma sebaceum and seizures is uncommon, imaging plays an important role in diagnosis of this condition.Sometimes intrauterine diagnosis of TS of the fetus can be suspected with visualization of cardiac rhabdomyomas in ultrasound.

Below are some of the features of TS detectable in plain CT, in a 16yr old patient.

Above image shows the presence of characteristic calcified and non-calcified sub-ependymal nodules (red arrows). Calcification of these subpendymal hamartomas is less frequent in early childhood, where as cortical/subcortical tubers can calcify as early as 2yrs of age.

Image showing multiple cortical and subcortical hypodensities suggestive of cortical tubers (blue arrows). Most of the tubers in TS are located in frontal lobe.

Left foramen of Monro region shows a relatively homogenous, non-calcified lesion (blue arrows) measuring AP dimension of ~13mm - suspicious of a Subpendymal Giant Cell Astrocytoma (SGCA / SEGA). These are considered WHO-Grade 1 tumors, eventhough there is a potential of causing obstructive hydrocephalus. These are theorized to evolve from the subpendymal nodules. Histologically both SGCA and subpendymal hamartomas show same appearance.SGCAs can show intense enhancement, and may show calcifications and heterogeneity.

Same lesion in sagittal reformat (golden arrow).

A few calcified cerebellar tubers (green arrows).

Above bone window images show multiple calvarial
small sclerotic areas of hyperostosis (orange arrows).

Acute Cholecystitis with intrahepatic perforation of GB causing secondary liver abscess

Above image shows distended gall bladder with pericholecystic fat stranding (orange arrow) consistent with acute cholecystitis.

Above post contrast CECT portal venous phase images showed focal small defect (yellow arrow) in the GB wall suggesting GB perforation, with abscess formation in segment V of right lobe. Blue arrow points to a single calculus within the GB lumen.

Serial axial sections showing small air pocket (orange arrow) within the liver, with adjacent heterogenous hypodense areas (yellow arrow),  superior to the hepatic abscess in segment V. If looked carefully complete pancreatic atrophy, with smooth duct dilatation and intraductal calculi can also be seen, consistent with Chronic Calcific Pancreatitis.

Eventhough acute cholecystitis is a common entity, GB perforation is rare and rarer still is its intrahepatic perforation. GB perforation is commoner in males. Risk of perforation is more in acalculous cholecystitis due to sepsis and associated co-morbidities.

Obstruction of cystic duct causes increased intraluminal pressure which inturn results in impared lymphatic and venous drainage. This results in vascular impairement leading to wall necrosis and finally perforation.

Niemeier classfied GB perforations into 3 types,
Type 1: Acute : Perforation with generalized biliary peritonitis.
Type 2: Subacute : Perforation with pericholecystic abscess and localized peritonitis.
Type 3: Chronic : Perforation with cholecysto-enteric fistula (Original classification did not include intrahepatic perforation / internal fistulae).

Treatment is with antibiotics and percutaneous drainage initially, followed by interval cholecystectomy. Open drainage and cholecystectomy has also been performed.



References:

Date RS, Thrumurthy SG, Whiteside S et al. Gallbladder perforation: case series and systematic review. Int J Surg 2012; : 63–68

Bilateral basal ganglia T1 hyperintensity

Left image shows normal T1 signal intensity of Globus Pallidus, where as
right T1 axial image in a 54yr old male with known chronic liver disease
 shows bilateral globus pallidus T1 hyperintensity.

 

Right image: Another CLD patient with bilateral T1 hyperintensity of Globus Pallidus.

Common causes of bilateral T1 hyperintense basal ganglia include:
1. Physiologic calcification.
2. NF-1
3. Hepatic Encephalopathy.
4. Hyperalimentation (Patients undergoing parenteral feeding).

Less common causes:
1.HIE (Term HIE, Hypoxic cerebral infarction).
2. CO poisoning.
3. Kernicterus.
4. Wilson's Disease.

Rarely thyroid / parathyroid hormonal imbalances, hypoglycemia, Fahr's disease, Hallervorden-Spatz syndrome, JE, Congenital HIV etc. also may cause T1 hyperintensity of the basal ganglia.

In chronic liver disease / cirrhotic patients there is symmetrical T1 hyperintensity in Globus Pallidus and Substantia Nigra.


References:
1. Expert-DDx Brain.

Hibernomas

A hibernoma is a rare benign fatty tumor arising from the vestiges (remnant / trace) of fetal brown fat. It is predominantly seen in 20-40 yrs age group with a slight female predilection. It is named so because of resemblance to brown fat in hibernating animals.

Most often the lesion is located in subcutaneous regions of the back (periscapular /interscapular region), neck, axilla, shoulder, thorax, thigh and retroperitoneum. Rarely these are also seen in scalp, breast, peri-ureteric region and scrotum.

Hibernoma usually manifest as slowly growing painless soft-tissue mass. Sometimes patient can be symptomatic due to compression of adjacent neuro-vascular structures, for example sciatica in a posterior thigh lesion.

In ultrasound these usually appear as hyperechoic lesions. Angiography will reveal lesional vascularity with arterio-venous shunting. These can mislead due to increased uptake in 18-FDG-PET.

In CT these lesions show low attenuating lesion, slightly higher attenuating than the subcutaneous fat. Enhancing septae may be seen, with lesion showing mild enhancement. MRI usually demonstrate lesion to be isointense to subcutaneous fat in most cases, with intervening enhancing sepatations. Reduced T1 and T2 signal intensity is also described in few cases. Contrast enhancement need not be present in all cases.

Additionally prominent lesional vessels may be seen in the ultrasound or as T2 flow voids in MRI, with can cause torrential hemorrhage during biopsy, especially in deep seated lesions.

Case courtesy of Dr Matt A. Morgan, Radiopaedia.org. From the case rID: 37589

Above image shows an intermuscular lesion between the gluteus medius and maximus muscles, with intermediate attenuation between fat and muscle. Prominent feeding vessel is seen along the lateral margin of the lesion.

Pre-operatively differentiating from liposarcomas is difficult. Four histological subtypes have been defined: Typical (~80%), Myxoid (8%), Lipoma-like and spindle cell variant. 'Typical' variant has predominantly brown fat. Myxoid variant is seen more often in men with higher water content (increased T2 signal). Lipoma-like lesion is seen more commonly in thigh, more resembling adult fat.


References:
Imaging Findings of a Hibernoma of the Neck
A.C.B.S. da Motta, D.E. Tunkel, W.H. Westra and D.M. Yousem
American Journal of Neuroradiology September 2006, 27 (8) 1658-1659;

CT and MR characteristics of hibernoma: six cases
Dursun, Memduh et al.
Clinical Imaging , Volume 32 , Issue 1 , 42 - 47

From the Archives of the AFIP
Benign Musculoskeletal Lipomatous Lesions
Mark D. Murphey, John F. Carroll, Donald J. Flemming, Thomas L. Pope, Francis H. Gannon, and Mark J. Kransdorf. RadioGraphics 2004 24:5, 1433-1466

Transient Synovitis of Hip Joint

Transient Synovitis (Coxitis fugax) is the most common cause of acute hip pain in children aged 3 to 10 years. It is a self-limiting acute inflammatory condition which is managed symptomatically. However it needs to be differentiated from Septic Arthritis, which will require antibiotics and surgical drainage.¹

Over 90% of hip joint effusions can be attributed to transient synovitis. ²
It has a male gender predilection and more frequently affects the right hip joint.

Etiology of transient synovitis remains unknown. Various theories include response to infection (URTIs), trauma, allergen / antigen etc. Clinical, laboratory and radiological findings help in differentiating Transient Synovitis from Septic Arthritis. The latter is usually associated with fever, elevated ESR & CRP.

X-Ray may reveal mild joint space widening due to effusion. Ultrasound is often the initial modality as it can reliably assess presence of joint effusion in the anterior recess.

MRI findings of Transient Synovitis include:
1. Joint effusion.
2. Synovial thickening & enhancement.
3. Adjacent soft tissue edema, with characteristic absent bone marrow edema.
4. Contralateral effusion (lesser volume usually).

Below MR images are of a 10yr old girl child with limping showing features of transient synovitis in right hip joint. No bone marrow edema or contra-lateral effusion is seen in this child. Grade 3 joint effusion is present in right hip joint.

Very rarely Transient Synovitis can cause osteonecrosis. But most often with analgesics and other symptomatic treatment, it resolves gradually, without any known long term sequelae. Eventhough it is most commonly seen in children, tranisent synovitis can also develop in adults.

Hip joint effusion is graded according to Mitchell Classification. 0 : None, 1 Minimal, 2 - Enough to surround the femoral neck and 3 distension of joint recesses.

References:

1. MR imaging of transient synovitis: Differentiation from septic arthritis. Pediatric Radiology, 2006.
2. Radiopedia.

Bilateral symmetrical enlargement of Lacrimal Glands

Causes of bilateral symmetrical enlargement of lacrimal glands include:

1. Sarcoidosis. (Usually associated with systemic sarcoidosis. Rare to have isolated lacrimal gland involement).
2. Lymphoma.
3. Leukemia.
 
Lymphomatous involvement of lacrimal glands usually shows restricted diffusion in MRI.

4. Sjogren Syndrome (autoimmune condition affecting salivary and lacrimal glands, F:M ratio of 9:1, seen in 4th and 5th decades of life, Early stages glands can become enlarged, to atophy in the later stages).


Less common causes of symmetrical lacrimal gland enlargement include:

5.  Mikulicz syndrome - Previously considered as a subtype of Sjogren, now being considered as a part of IgG4 related disease spectrum.

6. Kimura disease - usually presents as painless enlargement of neck lymph nodes and salivary glands, with associated blood eosinophilia, raised serum IgE, associated soft tissue masses. Affects males of 20-40yrs in 80% of cases.

7. Primary Lacrimal Amyloidosis.


Lacrimal glands measures ~4-5mm usually. A visual / subjective assessment is usually sufficient for making the diagnosis of enlargement.




References:
1. Lacrimal Glands: Size Does Matter!, Middle East Afr J Ophthalmol. 2011 Oct-Dec; 18(4): 328–330.
2. Radiopaedia.

ACL avulsion fracture

ACL avulsion fracture is the fracture of the tibial attachment of ACL at the anterior intercondylar region.

Zaricznyj modification of Meyers and McKeevers classification is the most used system, which divides these fractures into 4 types, with type 3 further divided into 3a and 3b.

Type 1 : Minimally / Non-displaced fragment.

Type 2 : Anterior elevation of the fragment.

Type 3 : Complete separation of the fragment.
   
         3a - Involves small portion of the eminence.
         3b - Majority of eminence is involved.

Type 4 : Comminuted avulsion or rotation of the fragment.

T1 WI showing Type 4 (Comminuted) Avulsion fracture in a 21yr male.

Type 3b ACL Avulsion fracture in an 18y female patient.