Renal Cyst Flashcards
(21 cards)
What are renal cyst?
And they can be divided into?
🔬 OVERVIEW: What Are Renal Cysts?
Renal cysts are fluid-filled sacs that can form anywhere in the kidney. They vary widely:
- Congenital vs acquired
- Benign vs potentially neoplastic
- Solitary vs multiple
- Simple vs complex
Because of this variability, renal cysts are:
- Common in both children and adults
- A diagnostic challenge, especially when complex or symptomatic
- Sometimes mistaken for tumors, requiring careful differentiation
What are they broad classification of renal cysts their Xteristics and examples
🧬 BROAD CLASSIFICATION
1. Congenital/Developmental (Non-neoplastic)
These are present at birth or arise due to abnormal kidney development. They can be solitary or part of a genetic syndrome. Examples:
- Multicystic dysplastic kidney
- Polycystic kidney disease (autosomal dominant or recessive)
2. Hereditary
These run in families and often affect both kidneys (bilateral). May eventually impair kidney function.
Examples:
- Autosomal Dominant Polycystic Kidney Disease (ADPKD): Adult form
- Autosomal Recessive Polycystic Kidney Disease (ARPKD): Infantile form
3. Acquired
Occur over time, usually in damaged kidneys (e.g. due to chronic renal failure or dialysis).
- Acquired cystic kidney disease (ACKD): Seen in long-term dialysis patients; associated with ⬆️ risk of RCC
Classify kidney cysts using potters classification.
🧪 POTTER’S CLASSIFICATION (Developmental Lesions)
Dr. Edith Potter proposed a classification to describe congenital cystic kidney diseases. She grouped them into:
Type I – Autosomal Recessive Polycystic Kidney Disease (ARPKD)
- Inheritance: Autosomal recessive
- Onset: In infancy/early childhood
- Kidney: Bilaterally enlarged, smooth external surface, tiny cysts (from collecting ducts)
- Clinical relevance: Presents with respiratory distress from pulmonary hypoplasia, renal failure, or Potter sequence in neonates.
Type II – Multicystic Dysplastic Kidney (MCDK)
- Developmental abnormality: Not inherited
- Kidney: Large, irregular, filled with non-communicating cysts of various sizes
- Usually unilateral
- Clinical relevance: Often detected on prenatal ultrasound. Non-functioning kidney. Bilateral cases are incompatible with life.
Type III – Autosomal Dominant Polycystic Kidney Disease (ADPKD)
- Inheritance: Autosomal dominant
- Onset: Adulthood (symptoms in 30s-50s)
- Kidney: Bilateral, massively enlarged, with cysts in all parts of the nephron
- Clinical relevance: Causes chronic kidney disease; associated with berry aneurysms, hepatic cysts, mitral valve prolapse.
What’s the clinical presentation of kidney cysts
🩺 CLINICAL PRESENTATION
While some renal cysts are silent and discovered incidentally, others can present with:
Symptom Explanation
Abdominal mass | Palpable enlargement, especially in large cystic kidneys (e.g. in ARPKD, ADPKD) |
Infection | Cysts can get secondarily infected—presents as fever, pain, sepsis
Respiratory distress / Seen in neonates with ARPKD due to pulmonary hypoplasia
Hemorrhage | Cysts may rupture and bleed—can cause hematuria or flank pain
Neoplastic transformation | Especially in acquired cystic disease of dialysis patients (risk of RCC) |
🔍 Summary
ARPKD (Potter I) | Tiny cysts, smooth kidney | Recessive | Infant death, pulmonary issues
| MCDK (Potter II) | Disorganized, cystic kidney | Sporadic | Often unilateral; benign if isolated
ADPKD (Potter III) | Large cysts, both kidneys | Dominant | Adult CKD, extra-renal cysts, aneurysms |
Acquired Cysts | Seen in ESRD/dialysis | None | ⬆️ Risk of RCC
Type | Key Features | Inheritance | Clinical Importance
🧭 OVERVIEW
Cystic kidney lesions are divided into non-neoplastic and neoplastic types. Understanding the difference is crucial for diagnosis, management, and predicting outcomes, especially because:
- Some mimic tumors on imaging
- Others are inherited or developmental
- A few can transform into malignancy
Now classify them into neoplastic and non neoplastic with examples Xteristics and clinical relevance.
A. NON-NEOPLASTIC CYSTIC LESIONS
These do not involve tumor cells, though some may arise in unusual settings (like dialysis). They include congenital, inherited, acquired, infectious, or traumatic cysts.
I. Renal Multicystic Dysplasia (Potter Type II)
- Developmental abnormality (not inherited)
- Kidney replaced by non-communicating cysts and disorganized parenchyma
- Often unilateral
- Clinical relevance: Often detected in utero; bilateral form incompatible with life due to absence of functioning nephrons.
II. Polycystic Kidney Disease (PKD)
- Adult (Autosomal Dominant) PKD – Potter Type III
- Genetic (AD inheritance)
- Bilateral kidney enlargement, multiple cysts from all nephron segments
- Onset: 30–50 years
-
Clinical relevance:
- Progresses to chronic kidney disease (CKD)
- Associated with berry aneurysms, hepatic cysts, and mitral valve prolapse
- Infantile (Autosomal Recessive) PKD – Potter Type I
- Genetic (AR inheritance)
- Tiny cysts in collecting ducts
- Onset: Perinatal
-
Clinical relevance:
- Presents in neonates with respiratory distress from pulmonary hypoplasia
- Often fatal if bilateral
III. Medullary Cystic Disease
- Medullary Sponge Kidney (MSK)
- Cystic dilatation of collecting ducts in renal papillae
- Often incidental finding on CT or IVU
-
Clinical relevance:
- Can be associated with nephrolithiasis, hematuria, UTIs
- Rarely leads to renal failure
- Nephronophthisis-Medullary Cystic Disease Complex
- Genetic tubulointerstitial disease
- Small, shrunken kidneys with corticomedullary cysts
-
Clinical relevance:
- Common genetic cause of end-stage renal disease in children
- Presents with polyuria, polydipsia, and growth retardation
IV. Simple Renal Cysts
- Most common renal cysts in adults
- Usually solitary, thin-walled, and benign
- Often asymptomatic, discovered incidentally on imaging
-
Clinical relevance:
- Must be differentiated from cystic RCC via imaging (Bosniak classification)
V. Acquired Renal Cysts
These develop due to external causes (disease, infection, trauma, etc.).
i. Dialysis-associated Cystic Disease
- Seen in long-term dialysis patients
- Multiple cysts develop in both kidneys
-
Clinical relevance:
- Increased risk of renal cell carcinoma
- Cysts may bleed, become infected, or rupture
ii. Hydatid Cyst (Echinococcosis)
- Caused by Echinococcus granulosus infection
- Rare renal involvement
-
Clinical relevance:
- Mimics tumors or abscesses
- Needs serologic tests and surgical removal
iii. Tuberculosis
- Renal TB can cavitate and form cyst-like lesions
-
Clinical relevance:
- Presents with sterile pyuria, hematuria
- May mimic tumors or abscess on imaging
iv. Renal Cell Carcinoma (with cystic degeneration)
- RCC may undergo central necrosis, appearing cystic
-
Clinical relevance:
- Must differentiate from benign cysts
- Imaging and biopsy are key
v. Traumatic Intrarenal Hematoma
- Results from renal injury
- Blood may organize and mimic a cyst
-
Clinical relevance:
- History of trauma helps
- Resolves or may need drainage
VI. Para-renal Cysts
Occur around the kidney, not within its parenchyma.
i. Pyelocalyceal Diverticula
- Outpouchings from calyceal system
- May collect urine or stones
-
Clinical relevance:
- Can cause infection, hematuria, or be confused with simple cysts
ii. Hilar Lymphangiectatic Cyst
- Dilated lymphatics in renal hilum
- Rare
-
Clinical relevance:
- Detected on imaging; can compress renal vessels or ureter
iii. Retroperitoneal Cysts
- Arise in retroperitoneum but may compress kidney
- Includes mesenteric or lymphatic origin
iv. Perinephric Pseudocyst (from trauma)
- Encapsulated fluid collection around kidney
- Due to urine leak or hematoma after trauma or surgery
B. NEOPLASTIC CYSTIC LESIONS
These are true tumors with cystic components. Diagnosis requires histology to confirm neoplastic nature.
I. Cystic Nephroma
- Benign tumor with multilocular cysts
- Often in children (boys) or middle-aged women
-
Clinical relevance:
- May mimic Wilms’ tumor or RCC on imaging
- Requires surgical excision
II. Cystic Partially Differentiated Nephroblastoma (CPDN)
- Variant of Wilms’ tumor
- Seen in young children
-
Clinical relevance:
- Shares imaging features with benign cystic nephroma
- Histology reveals immature nephrogenic elements
III. Multifocal Cystic Change in Wilms’ Tumor
- Wilms’ tumor may contain necrotic/cystic areas
-
Clinical relevance:
- Presence of cysts doesn’t exclude malignancy
- Requires nephrectomy and staging
🔍 Summary Table
Category Subtype Key Feature Clinical Importance
Non-neoplastic | ADPKD, ARPKD Genetic, cystic kidneys | CKD, aneurysms, pulmonary issues
Developmental | MCDK Disorganized cysts | Unilateral usually benign
Acquired | Dialysis, TB, Trauma | From disease or infection | RCC risk, mimic tumors
Neoplastic Nephroma, CPDN | True tumors | Require surgery, histology
What’s the most common renal cystic dexs on newborns?
MCKD
Define MCKD & it’s features
🧠 DEFINITION
Multicystic Renal Dysplasia (MCRD) is a developmental disorder where the kidney is replaced by a disorganized, cyst-filled mass due to abnormal differentiation of the metanephric blastema and ureteric bud.
- It’s non-hereditary in most cases, though it can occur in syndromes.
- Potter classified it as Type II in the spectrum of cystic kidney diseases.
- Most common cystic renal disease in newborns and infants.
What’s the🔬 PATHOGENESIS of MCKD?
What are the associate abnomalities seen with it?
- The metanephric blastema (future nephrons) and the ureteric bud (collecting system) fail to interact properly.
- As a result, nephron development is halted, and instead, you get:
- Undifferentiated mesenchyme
- Primitive ducts
- Cysts (dilated tubules)
The abnormal differentiation is often due to obstruction in the urinary tract, especially early in development.
⚠️ ASSOCIATED OBSTRUCTIVE ABNORMALITIES
Commonly associated with:
- Pelviureteric junction (PUJ) obstruction
- Ureteral atresia
- Urethral obstruction (e.g., posterior urethral valves)
These lead to urine backup, increasing pressure and disrupting normal nephron development.
What are the types of MCKD and their👶 CLINICAL FEATURES of MCKD? & prognosis
- Unilateral MCRD
- Most common form
- Presents as a flank mass in newborns or infants
- Often discovered incidentally on prenatal or postnatal ultrasound
- Associated anomalies may include:
- Ventricular septal defect
- Tracheoesophageal fistula
- Lumbosacral meningomyelocele
- Down syndrome
👉 Prognosis: Excellent after surgical removal of the dysplastic kidney
- Bilateral MCRD
- Rare and fatal unless treated with renal transplant
- Leads to oligohydramnios in utero ⬆️ pulmonary hypoplasia ⬆️ respiratory failure at birth
What are the 🔍 MORPHOLOGIC FEATURES of MCKD?
🔍 MORPHOLOGIC FEATURES
GROSS
- Kidney is enlarged, irregular, and multicystic
- Resembles a bunch of grapes
- Cysts are non-communicating
- Renal pelvis and calyces are usually absent or malformed
- Ureter is often absent, atretic, or obstructed
MICROSCOPIC
-
Undifferentiated mesenchyme with:
- Smooth muscle
- Cartilage (a key diagnostic clue)
- Primitive ducts
-
Dilated tubules lined by flattened epithelium
- Surrounded by collagen and fibrous tissue
- Scanty or absent glomeruli
- No well-formed nephrons
📌 KEY DIFFERENTIALS
Condition Key Difference
Hydronephrosis /Cysts communicate with pelvis; calyceal dilatation present
ARPKD | Bilateral, uniformly enlarged kidneys with radial cysts
Simple renal cyst |Solitary, thin-walled, often in adults
Wilms’ tumor | Solid mass with primitive blastemal cells
📚 CLINICAL PEARLS
- Always consider MCRD when you see a unilateral multicystic kidney in a neonate.
- In bilateral cases, suspect Potter sequence: oligohydramnios ⬆️ flattened face, limb deformities, lung hypoplasia.
- No nephrectomy is needed for asymptomatic unilateral cases unless there’s hypertension, infection, or suspicion of malignancy.
Define ADPKD
ADPKD is a hereditary, bilateral renal disorder where multiple cysts gradually replace the renal parenchyma, causing:
- Progressive renal enlargement
- Loss of nephron function
- Eventual chronic kidney disease and end-stage renal failure (ESRD)
📊 EPIDEMIOLOGY
- Affects 1 in 400 to 1,000 live births
- Accounts for 5–10% of ESRD cases needing dialysis or transplant
- Autosomal dominant inheritance with high penetrance
ADPKD is caused by mutations in:
List them and it’s severity, and frequency.
🧬 GENETICS AND PATHOGENESIS
ADPKD is caused by mutations in:
Gene . Chromosome . % of Cases . Severity
PKD1 | 16p13.3 | \~85% | More severe
PKD2 | 4q21 | \~15% | Milder, slower progression |
🧩 Mechanism:
- Follows a “two-hit” hypothesis (like tumor suppressor genes):
- First hit: Inherited germline mutation (dominant)
- Second hit: Acquired somatic mutation in renal tissue
> Both alleles must be non-functional in a given nephron for cyst formation to begin.
What’s the 🔁 Pathophysiology: of PKD?
2 HIT SYSTEM
🔁 Pathophysiology:
- Mutations affect polycystin-1 (PKD1) or polycystin-2 (PKD2) proteins
- These proteins normally regulate:
- Tubular structure
- Calcium signaling
- Cilia function in renal epithelium
- Loss of function leads to:
- Abnormal tubular cell proliferation
- Fluid secretion
- Cyst formation and expansion
🧪 DISEASE PROGRESSION
- Disease is bilateral; unilateral cases are likely misclassified multicystic dysplasia
- Cysts begin in a minority of nephrons
⬆️ Function is preserved until 4th–5th decade - Then progressive enlargement compresses and destroys nephrons ➡️ renal failure
📈 Renal Failure Risk Over Time:
. Age . PKD1 Mutation . PKD2 Mutation
40 yrs | <5% | <5% |
50 yrs | >35% | \~15% |
60 yrs | >70% | \~45% |
70 yrs | >95% | \~65–70% |
🩺 CLINICAL RELEVANCE
-
Diagnosis is often delayed until adulthood unless:
- There’s family history
- Or cysts are found on imaging for another issue
- Can present with:
- Hypertension (from renin-angiotensin activation)
- Hematuria
- Flank pain
- Recurrent UTI or nephrolithiasis
- Enlarged kidneys on palpation
What’s the differential diagnosis of PKD?
🔍 DIFFERENTIAL DIAGNOSIS
.Condition . Key Differentiator .
ARPKD | Infantile onset, smaller radial cysts, liver involvement |
Multicystic dysplasia | Non-hereditary, unilateral, congenital
Simple renal cysts | Asymptomatic, isolated, no family history
Acquired cystic disease | Seen in long-term dialysis patients
🧠 CLINICAL PEARLS
- Screen first-degree relatives via ultrasound (age-dependent cyst criteria)
- Manage blood pressure aggressively to slow progression
- Tolvaptan, a vasopressin V2 receptor antagonist, can slow cyst growth
- Monitor for extrarenal manifestations:
- Liver cysts
- Intracranial aneurysms (risk of subarachnoid hemorrhage)
- Mitral valve prolapse
- Colonic diverticulosis
