Flank pain: case presentation and MCQ

History:
Flank pain

Images:

Question:
1- Which choice best fits the findings involving the L kidney? 

A    Renal cell carcinoma. 
B    Renal lymphoma. 
C    Urinoma. 
D    Hematoma. 
E    Abscess. 

	2- Here is an ultrasound image obtained the day before the CT. Which choice most likely describes the history?
A	Tuberous sclerosis.
B	Gunshot wound.
C	Acute urinary obstruction.
D	Encounter with nephrologist.
E	Renal vein thrombosis.

For the question: "Here is an ultrasound image obtained the day before the CT. Which choice most likely describes the history?" 

Here is some ultrasound images obtained AFTER the CT

	3- Please respond to the following with TRUE or FALSE.
T or F	There is evidence for an AV fistula.
T or F	There are elevated velocities of the arcuate arteries.

Answers

1- D: Hematoma (Large perinephric hematoma)

2- D: Encounter with nephrologist (Correct. The patient has a complex history and presented with renal failure. Patient underwent left renal core biopsy under ultrasound guidance (needle visible on the image), and the next day began experiencing left sided flank pain. (Nice job! You gave the correct answer on the first try.) 

3- For the T/F Question: "There is evidence for an AV fistula." 

For the T/F Question: "There are elevated velocities of the arcuate arteries." 

Findings:

Initial image demonstrates core biopsy needle sampling the left kidney.

CT without contrast demonstrates heterogeneously hyper dense material effacing the left kidney and left perirenal space. Other findings unrelated to kidney:  Changes of diffuse mesenteric edema.  Postsurgical changes consistent with the prior multivisceral transplant are seen, with some altered enteric anatomy.  Small bowel wall thickening.

Ultrasound demonstrates heterogeneous echo texture of the left renal fossa.  Doppler ultrasonography demonstrates an arcing, anomalous renal arterial to renal venous connection within the left kidney.  There are elevated velocities of the arcuate arteries in the mid left kidney.  There is a mildly elevated resistive index of the main renal artery, measuring 0.81.

Diagnosis:  Left renal biopsy complicated by perinephric hematoma and AV fistula

Key points:

• Percutaneous organ biopsy has a relatively low rate of major complications. In the radiology literature, the rate of major hemorrhage associated with kidney biopsy has been reported to be as low as 0.7% (1).
• Renal arteriovenous (AV) malformations can be congenital or acquired; the acquired variety are typically referred to as AV fistulas (AVF). The most common cause of AVF is iatrogenic (>15% of renal biopsies), followed by trauma. Patients with pre-existing hypertension are thought to be at greater risk for AVF following biopsy.
• Commonly a patient will present with hematuria or renal colic. On physical exam, a bruit may be auscultated. The fistulas will often close spontaneously, and thus conservative treatment is standard. Larger AVF can induce hypertension and/or CHF, and rarely a patient may also present with hypotension secondary to hemorrhage; in these types of situations,  transcatheter embolization (as selective as possible) is the typically preferred management. Surgical resection is reserved for malignant AVF, as well as AVF not responsive to embolization.
• Catheter, CT or MR angiography can be utilized to diagnose AVF, with visualization of direct arterial to venous communication, with an early draining vein. Pseudoaneurysm formation and hematoma may also be indentified. Doppler Ultrasound may also be able to identify a direct arterial to venous communication, as well as arterialized flow of the draining vein.

References:

1.  Atwell, T et al. Incidence of Bleeding After 15,181 Percutaneous Biopsies and the Role of Aspirin. AJR 2010; 194:784-789.

2.  Cardella, J et al. Quality Improvement Guidelines for Image-guided Percutaneous Biopsy in Adults. J Vasc Interv Radiol 2003; 14:S227–S230.

3.  Wakefield M, et al. Renal Arteriovenous Malformation. eMedicine.medscape.com. Updated 3/10/2009.

4.  Walker T. Dx: Renal Arteriovenous Fistula. StatDx.com. Amirsys, Inc. 2005-2011.