Kidneys

Renal cysts

The Bosniak classification system was designed to separate cystic renal masses into surgical and nonsurgical categories by analysis of specific CT features.

Category I: Category I lesions are simple benign cysts showing homogeneity, water content, and a sharp interface with adjacent renal parenchyma, with no wall thickening, calcification, or enhancement.

Category II: This category consists of cystic lesions with one or two thin (<=1 mm thick) septations or thin, fine calcification in their walls or septa (wall thickening > 1 mm advances the lesion into surgical category III) and hyperdense benign cysts with all the features of category I cysts except for homogeneously high attenuation. A benign category II lesion must be 3 cm or less in diameter, have one quarter of its wall extending outside the kidney so the wall can be assessed, and be nonenhancing after contrast material is administered.

Category IIF: This category consists of minimally complicated cysts that need followup. This is a group not well defined by Bosniak but consists of lesions that do not neatly fall into category II. These lesions have some suspicious features that deserve followup to detect any change in character.

Category III: Category III consists of true indeterminate cystic masses that need surgical evaluation, although many prove to be benign. They may show uniform wall thickening, nodularity, thick or irregular peripheral calcification, or a multilocular nature with multiple enhancing septa. Hyperdense lesions that do not fulfill category II criteria are included in this group.

Category IV: These are lesions with a nonuniform or enhancing thick wall, enhancing or large nodules in the wall, or clearly solid components in the cystic lesion. Enhancement was considered present when lesion components increased by at least 10 H.

LINKS:

http://www.radiologyassistant.nl/en/44d1045b472df

(Text main source: www.radswiki.net)

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Renal oedema

Reduced echogenicity on US, which is especially prominent in the renal pyramids which appear anechoic and maybe mistaken for cysts. Renal capsule nay appear unusually prominent. A transient increase in parenchymal echogenicity due to disruption of tissue interfaces.

Etiology: Acute GN, Acute PN, Nephrotic sy., Transplant rejection, Renal contusion.

LINKS:

http://www.ceb-institute.org/fileadmin/upload/refman/Ultraschall_Med_2006_27_141_Thalhammer.pdf

(Text main source: Differential diagnosis in Abdominal US-Saunders)

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The transplanted kidney

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Renal calcifications

Types of calcifications:

- Medullary calcifications (95% of all parenchymal calcifications)

- Cortical calcifications

- Calcifications in a cyst wall, usually a complicated cyst (3%)

- Calcification in a renal tumour is usually amorphous but can be ring like and mimic cyst wall calcification (6% of renal tu.'s)

Medullary Ca:

Due to any cause of hypercalcemia, hypercalciuria. Pyramid margins are echogenic while the center remain echolucent. The pyramids may be echogenic and may shadow.

Cortical Ca:

5% of parenchymal calcification. Secondary pyramidal calcification may occure.