Fatty Liver

Axial "in-phase" MR image shows increased signal intensity of the liver.

Axial "opposed-phase" MR image shows decreased signal of the entire liver when compared with the same areas on in-phase image. 

Facts

• Triglyceride accumulation within cytoplasm of hepatocytes
• Can be due to alcoholic liver disease, nonalcoholic fatty liver disease, viral hepatitis, drugs
• May progress to steatohepatitis and cirrhosis
• Avoid the use of "fatty infiltration of the liver", which is misleading because fat deposition in Fatty Liver is in hepatocytes - rarely in other cell types
• Sensitivity/specificity for detection:
• Ultrasound = 60-100% / 77-95%
• Non-contrast CT = 43-95% / 90%
• Chemical-shift MRI = 81% / 100%

MR Imaging

• Because protons in water and fatty acid molecules precess in different resonance frequency, proton chemical shift imaging can be utilized to image this difference
• If images are obtained when fat and water protons are "in-phase", their signals are additive (brighter). If they are "out-of-phase", their signals cancel each other (structure becoming darker)
• Amount of hepatic fat can be quantified by assessing the degree of signal loss

Reference

Hamer OW, Aguirre DA, Casola G, et al. Fatty liver: imaging patterns and pitfalls. Radiographics 2006; 26:1637-1653.

Focal Urinary Bladder Wall Thickening

Axial and sagittal-reformatted CT images show focal thickening of the posterior wall of the urinary bladder (arrows) with increased enhancement relative to normal bladder wall. 

Differential Diagnosis

• Tumor (benign, malignant, metastasis)
• Adherent clot
• Infection/inflammation (TB, cystitis cystica/glandularis, malakoplakia, schistosomiasis)
• Trauma (mural hematoma)
• Extravesical pathologies (spread of extravesical inflammation or tumor, endometriosis)

Facts

• Transitional cell carcinoma accounts for most focal bladder masses
• Most of the time it is impossible to distinguish tumor from other causes of focal wall abnormality and cystoscopy is necessary

Our case: Transitional cell carcinoma in a 73-year-old female

Reference

Patel U. Imaging And Urodynamics Of The Lower Urinary Tract. Springer 2010.

Bhargava. Ultrasound Differential Diagnosis. Jaypee Brothers Publishers, 2005.

Krukenberg Tumors

Axial and coronal-reformatted CT images of a 41-year-old woman shows an enlarged, solid-appearing right ovarian mass (arrows). The left ovary (not shown) is normal. 

Facts:

• Metastatic tumor to the ovary that contains mucin-secreting, signet ring cells
• Usually originate from primary tumors of GI tract (most common = colon and stomach)
• 10% of all ovarian tumors
• Occur in reproductive age

Imaging:

• Nonspecific appearance. Can be solid or mixed solid/cystic
• High suspicion for ovarian metastasis if:
• Bilateral 
• Complex-appearing ovarian masses
• Known GI tract tumor (esp. colon and stomach)
• MRI showing T1/T2 hyper intensity due to mucin

Our case: Ovarian metastasis from primary gastric cancer.

Reference:

Jung SE, et al. CT and MR imaging of ovarian tumors with emphasis on differential diagnosis. Radiographics 2002; 22:1305.