Renal Cystic Disease, Part IV

Question 1

Simple Cysts

Answer 1

Thought to originate from distal convoluted tubule or collecting ducts

Increasing prevalence with increasing age

Question 2

Simple Cysts

Answer 2

Male-to-female predominance: 2 to 3:1
Associated with smoking, HTN, reduced renal mass, increased body mass index, reduced kidney function

Similar to ADPKD, circulating levels of copeptin levels (validated surrogate for vasopressin) is associated with kidney length and function.

Question 3

Simple Cysts

Answer 3

Generally asymptomatic, but may be associated with HTN, erythrocytosis

Infected cysts may develop thickened walls, calcifications.

Question 4

Simple Cysts

Answer 4

Large cysts associated with severe HTN may be considered for drainage.

Kidney transplantation: Growth rate of simple cysts does not increase with kidney donation whether they are in the donor or recipient. Simple cysts do not adversely affect renal outcomes.

Question 5

Acquired Cystic Kidney Diseases

Conditions Associated with Acquired Cystic Kidney Diseases

Answer 5

Chronic hypokalemia: cysts typically localized to renal medulla; resolution possible after correction of hypokalemia (e.g., adrenalectomy for functioning tumors)

Question 6

Acquired Cystic Kidney Diseases

Conditions Associated with Acquired Cystic Kidney Diseases

Answer 6

CKD-associated acquired cystic kidney diseases (ACKD)

Development of >3 to 5 macroscopic cysts in individuals without a hereditary cystic disease is required for the diagnosis of ACKD. ACKD typically involves >25% of renal parenchyma.

Question 7

Acquired Cystic Kidney Diseases

Conditions Associated with Acquired Cystic Kidney Diseases

Answer 7

Increased risks with CKD vintage, 80% to 100% have ACKD by 10 years on dialysis.

May regress with successful kidney transplant

Question 8

Acquired Cystic Kidney Diseases

Conditions Associated with Acquired Cystic Kidney Diseases

Answer 8

ACKD may transform into adenomas and RCC

1. Unlike sporadic clear cell RCC, ACKD-associated RCC are typically multifocal and bilateral with lower proliferative activity and metastatic disease.
2. ACKD-associated RCC are histologically distinct with eosinophilic cytoplasm with calcium oxalate crystal deposits in cribriform, tubulocystic, and papillary architecture.

Question 9

Acquired Cystic Kidney Diseases

Conditions Associated with Acquired Cystic Kidney Diseases

Answer 9

Annual ultrasound screening (or at least 3 years after onset of dialysis with frequency increased to every 1 to 2 years if ACKD is present) is indicated in ESRD patients with good life expectancy. Interpretation is generally based on Bosniak classification.

Question 10

Acquired Cystic Kidney Diseases

Bosniak classification of cysts (initially defined for CT, now often used for ultrasound):

Answer 10

I: Benign simple cyst; hairline thin wall; no septation, calcification, or solid components; no enhancement with contrast CT

Question 11

Acquired Cystic Kidney Diseases

Bosniak classification of cysts (initially defined for CT, now often used for ultrasound):

Answer 11

II: Benign cyst with a few hairline thin septations ± “perceived” enhancement may be present; fine calcification in cyst wall or septation(s). Uniformly high-attenuation lesions < 3 cm, well marginated; no enhancement with contrast CT

Question 12

Acquired Cystic Kidney Diseases

Bosniak classification of cysts (initially defined for CT, now often used for ultrasound):

Answer 12

IIf (f is for follow-up): Cysts with multiple hairline thin septa or minimal smooth thickening of wall/septa; “perceived” enhancement of septa/wall; calcification of wall/septa that may be thick and nodular; no measurable contrast enhancement.

Question 13

Acquired Cystic Kidney Diseases

Bosniak classification of cysts (initially defined for CT, now often used for ultrasound):

Answer 13

III: “Indeterminate” cystic masses with thickened irregular or smooth wall/septa; measurable enhancement. Contrast enhancement implies vascularized mass, thus possible malignancy. Although possibly benign, surgery is generally indicated.

Question 14

Acquired Cystic Kidney Diseases

Bosniak classification of cysts (initially defined for CT, now often used for ultrasound):

Answer 14

IV: Malignant cystic masses that also contain enhancing soft tissue components

Question 15

Acquired Cystic Kidney Diseases

General management per Bosniak classification:

Answer 15

Class I and II are benign. Six- to twelve-month follow-up may be warranted in ESRD patients.

Class IIf requires follow-up within 3 to 6 months.

Question 16

Acquired Cystic Kidney Diseases

General management per Bosniak classification:

Answer 16

Class III and IV are considered malignant until proven otherwise. Surgical evaluation is required.

Management: bed rest, analgesics; if no resolution, consider renal embolization or laparoscopic nephrectomy.

Question 17

Multilocular Cystic Nephroma, a.k.a. Papillary Cystadenoma, Benign Cystic Nephromas

Answer 17

Well-circumscribed, multiseptated, generally benign, cystic lesions typically classified as Bosniak III on CT that require surgery to exclude malignancy.

Question 18

Multilocular Cystic Nephroma, a.k.a. Papillary Cystadenoma, Benign Cystic Nephromas

Answer 18

Thought to arise from hamartomatous origin, embryonic metanephric blastema, or variant of Wilms tumor.

Question 19

Multilocular Cystic Nephroma, a.k.a. Papillary Cystadenoma, Benign Cystic Nephromas

Answer 19

Follows a bimodal age and sex pattern: boys 3 months to 4 years; women 40 to 60 years of age.

Question 20

Multilocular Cystic Nephroma, a.k.a. Papillary Cystadenoma, Benign Cystic Nephromas

Answer 20

Complications: flank pain, hematuria, calculi, urinary tract infections. Carcinomatous degenerations may occur.

Question 21

Glomerulocystic Kidney Disease

Answer 21

Glomerulocystic kidney disease (GCKD) may be present as a familial dominant or sporadic condition or infantile manifestation of ADPKD. GCKD is characterized by cystic dilation involving Bowman space and proximal tubules.

Question 22

Glomerulocystic Kidney Disease

Answer 22

Ultrasound may be notable for increased echogenicity of renal cortex with minute cysts. Associated renal medullary dysplasia and biliary dysgenesis may be found in infants with familial or sporadic GCKD.

Question 23

Glomerulocystic Kidney Disease

Answer 23

GCKD can present as an isolated condition or as part of a disease syndrome involving a heritable malformation syndrome or dysplastic kidneys. Familial hypoplastic GCKD presents with relatively small kidneys with medullocalyceal abnormalities and variable associations with gynecologic abnormalities and maturity-onset diabetes of the young type 5 (MODY5).