Renal Cysts

20may6

Somebody consulted me with this report:

RENAL CYSTS

Critical question:

Are the renal cysts on ultrasound highly suspicious for malignancy?

If yes, a urologist should be consulted who most likely will recommend cancer treatment such as surgery (nephrectomy).

If no, if asymptomatic, just watch and wait. No medical intervention or procedure. Watch and wait includes self-monitoring for symptoms and may do imaging procedures at planned interval (say 6 months after the first ultrasound).

If no, but symptomatic, just as complicated with infection or hemorrhage, a urologist should be consulted who may recommend some procedures like aspiration, sclerotherapy and excision of cyst.

When to suspect malignancy in renal cysts?

Bosniak Classification of Renal Cystic Disease (based on CT Scan)

Ultrasound Classification Correlated with Bosniak’s Classification

A systematic approach should be applied to initially identify unilocular and multilocular cysts.

In unilocular cysts, those with solid components will fall into Category III or IV, then contrast-enhanced US, CT, or MRI should be arranged.

For those without solid components, calcification patterns and septa or wall thickening should be interpreted next.

Renal cysts without calcifications, septa, or wall thickenings shall be classified into Category I.

Category II cysts have fine calcifications in short segments or slightly thickened calcifications on the cystic wall, whereas Category IIF lesions have thick or nodular calcifications.

Calcifications that are greater in number or size do not warrant upgrade to anything above Category IIF unless solid soft tissues appear. Therefore, calcification does not affect the differentiation between masses that are in Categories IIF and III.

Category II lesions have regular and hairline-thin septa. Category IIF lesions have smoothed multiple hairline-thin septa. Warren and McFarlane suggest that if the wall or septa thickness exceeds 1 mm, it is a sign of malignancy. However, other authors suggest that walls or septa of “more than hair-line thin” thicknesses favor malignancy. Accurate measures are difficult to obtain; some interindividual or intraindividual differences in measurements can be found.

A unilocular cyst with slightly irregular and grossly thickened (≧ 2 mm) septa falls into Category III, and contrast-enhanced US, CT, or MRI is required. Wall thickening in cystic lesions can also be seen in hemorrhagic cysts, infected cysts, or abscesses. Sometimes it is difficult to differentiate cysts from tumors using US; therefore, patient history is important for the differential diagnosis and follow-up or intervention is needed.

Multilocular cysts separated from the normal renal parenchyma and lacking solid components can be classified into Category IIF. Contrast-enhanced US, CT, or MRI is required when cysts have solid components.

A multilocular Category III cyst is an encapsulated cystic mass containing numerous thickened smooth or slightly irregular septa and uniform smooth or slightly irregular wall thickening. The cyst wall and septa are grossly thickened (≧ 2 mm), but vascularity in soft tissue components is not enhanced or increased. If it is, the cyst will be classified into Category IV. Multilocular cystic renal masses with lobulated contours but no soft tissue components shall be classified into Category III.

Characterization and management of various renal cystic lesions by sonographic features

Journal of the Chinese Medical Association

Volume 81, Issue 12, December 2018, Pages 1017-1026

https://www.sciencedirect.com/science/article/pii/S1726490118301746

The average size of Stage I renal cysts are 5–10 mm in diameter, though they can be larger [4]. While the original definition of a Stage I renal cyst does not include size, the revised Bosniak renal cyst classification system highlights a diameter of ≥3 cm as worthy of follow-up and utilizes this size among the features to distinguish between a Stage II or IIF cyst [10].

Renal cysts

Incidence

Autopsy studies in patients over the age of 50 reveal greater than a 50% chance of having at least one simple renal cyst.1 In 1983, using early computed tomography (CT) scan technology, renal cysts were discovered in 33% of patients in the same age group.2

One third of people older than 50 years develop renal cysts.

Simple cysts are the most common cystic renal lesions; they are present in 5% of the general population, increasing in frequency to 25-33% of patients older than 50 years, and account for 65-70% of renal masses

Causes

• • Developmental – Multicystic dysplastic kidney(MCDK)

  • Genetic – Autosomal recessive polycystic kidney disease(ARPKD), autosomal dominant polycystic kidney disease (ADPKD), juvenile nephronophthisis (JNPHP), medullary cystic kidney disease (MCKD), glomerulocystic kidney disease (GCKD)

  • Cysts associated with systemic disease – Von Hippel-Lindau syndrome(VHLS), tuberous sclerosis (TS)

  • Acquired – Simple cysts, acquired cystic renal disease, medullary sponge kidney(MSK)

  • Malignancy – Cystic renal cell carcinoma(RCC)

Clinical classification:

• • Simple cysts

  • Complicated cysts

Renal cysts, in general, may be classified as “simple” or “complex.” “Simple” cysts are best defined using sonographic criteria. These include: (1) absence of internal echoes, (2) posterior enhancement, (3) round/oval shape and (4) sharp, thin posterior walls.4 When all of the criteria are met, the cyst is benign and no follow-up is required. The difficulty arises when cysts do not meet the rigid characteristics of the “simple” definition.

What are renal cysts?

Renal cysts are sacs of fluid that form in the kidneys. Most of the time, they are simple kidney cysts, meaning they have a thin wall and only water-like fluid inside. They are fairly common in older people and typically do not cause any symptoms or harm.

The cause of renal cysts is not known, although age is a major risk factor. An estimated one-third of people older than age 70 have at least one simple renal cyst. It can be normal to have more than one simple cyst in each kidney, especially with increasing age.

Having a few simple renal cysts is different from having many cysts in the kidneys because of polycystic renal disease (PKD). PKD is a genetic disorder characterized by clusters of cysts that can impair kidney function.

How are renal cysts diagnosed and evaluated?

Since they rarely cause symptoms, renal cysts are most often found during imaging tests performed for other reasons. In such cases without any symptoms, simple renal cysts are usually left alone and do not need any further tests. However, some renal cysts look more complex than the usual simple renal cyst. These complex renal cysts can have a thicker wall, or solid material inside instead of just fluid. Once complex renal cysts are discovered, additional imaging tests may be performed to monitor them and distinguish benign cysts from cancer.

How are renal cysts treated?

Renal cysts generally do not require treatment unless they are causing symptoms or harming kidney function. Treatment options include:

• • Sclerotherapy: Also known as percutaneous alcohol ablation, sclerotherapy involves the insertion of a long needle through the skin and into the cyst under ultrasound guidance. The doctor will drain the cyst and fill it with an alcohol-based solution that causes the tissue to harden and shrink, reducing the chance of recurrence. The procedure is usually performed on an outpatient basis with a local anesthetic.

  • Surgery: For larger cysts, a surgeon will make a small incision and access the cyst with a laparoscope. The surgeon will then drain the cyst and burn or cut away its outer layer. Laparoscopic surgery requires general anesthesia.

ROJ@20may6