Cystic Diseases Flashcards
What is a cyst?
Abnormal fluid-filled epithelial-lined, dilated sac that arises within the renal parenchyma from an existing tubule or collecting duct
Pseudo-cytsts have no epithelial lining
Cystic kidneys are arbitrarily defined as kidneys with 3 OR MORE CYSTS
Some cysts are incompatible with life, some remain stable, and may be confused with malignant tumors!
AUTOSOMAL DOMINANT POLYCYSTIC KIDNEY DISEASE?
Fairly common, characterized by the presence of EXPANDING, BILATERAL RENAL CYSTS
3-4 cm wide cysts with little intervening stroma, filled with clear fluid and lined by epithelia (TRUE cysts)
Parenchyma between cysts may be FUNCTIONAL and is YELLOW, not purulent (no pus)
Functioning nephrons between the cysts
Clinical presentation of ADPKD
Late onset (ADULTS ONLY)
Can affect multiple systems
Insidious onset
HEMATURIA, HTN, PAIN – kidneys are large and expanded, may give a “dragging sensation”
Extra-Renal Symptoms –> LIVER CYSTS (40%, moreso with age) derived from biliary epithelium –> pancreas, spleen, seminal vesicles may show cysts too
Increased risk of INGUINAL HERNIAS
BERRY ANEURYSMS!!!!!!! And mitral valve prolapse –> two potential manifestations!
Asymptomatic until the cysts DESTROY THE RENAL PARENCHYMA and eventually cause RENAL INSUFFICIENCY/FAILURE –> patients don’t present until this point!
Elevated creat/BUN (azotemia), PROTEINURIA (nephrotic), Uniformly bilateral
Genetics of ADPKD
Mutations in PKD1 and PKD2
80% of the time PKD1 which is MORE SEVERE than PKD2 –> PKD1 is VERY LIKELY TO DEVELOP RENAL FAILURE
These genes encode proteins POLYCYSTIN 1 and POLYCYSTIN 2 –> Polycystin 1 is a transmembrane protein that suppresses proliferation –> mutation leads to hyperplasia of epithelial cells that secrete substances that fill cysts and cause inflammation and fibrosis
Polycystin 2 –> localized in cilia and has a mechanosensory function, as well as fxns related to calcium transport
Progression and Outcome of ADPKD
Most people PROGRESS TO CHRONIC RENAL FAILURE (PKD1 mutation is much faster to progress - affects in 50s, PKD2 is in 70s)
Cause of death includes extra-renal issues –> SUBARACHNOID HEMORRHAGE FROM BERRY ANEURYSMS!!!!, cardiac disease (HTN related) or infection
Increased risk of BILATERAL RENAL CELL CARCINOMA!
AUTOSOMAL RECESSIVE PKD
Disease of CHILDREN! Neonates, early childhood (like most recessive conditions)
HIGH neonate mortality (25-35%)
Significant cause of LIVER and KIDNEY morbidity/mortality in children
Characterized by FUSIFORM, dilated collecting tubules lined by undifferentiated epithelium
Grossly, kidneys are ENLARGED with SMOOOOOOTH surface and a SPONGY inner surface –> cysts not obvious and have a LACY appearance, lined by cuboidal epithelium
Cut surface shows ELONGATED CHANNELS that REPLACE CORTEX and MEDULLA (elongated cylindrical cysts) – Long, narrow cysts!
Cylindrical dilation of collecting tubules
BILATERAL DISEASE
Genetics of ARPKD
Mutation to PKHD1 which encodes for fibrocystin (kidney, liver, pancreas) –> this is a large transmembrane protein that likely serves as a receptor with a role in differentiation
Presentation of ARPKD?
Majority found in utero or shortly thereafter
Thoracic cavity is VERY SMALL BECAUSE OF ENLARGED LIVER/KIDNEYS
Since kidneys produce AMNIOTIC fluid from fetal urine, a NON-FUNCTIONING kidney will result in LESS CUSHIONING in the womb and COMPRESSION of the FETUS –> facial deformities, other malformations possible
Dominant issue is the LUNGS –> increased pressure from the large kidneys STUNTS LUNG GROWTH –> hypoplastic lungs!!!!
“Potter Sequence” Rocker bottom Feet and deformed facies secondary to OLIGOHYDRAMNIOS (low amniotic fluid)
Congenital HEPATIC FIBROSIS
HTN often seen (80%), may be severe
HEPATOSPLENOMEGALY in older kids
Prognosis and Outcome of ARPKD?
Majority DIE in the neonatal period!
50% of survivors –> ESRD
HTN, renal failure, portal HTN, liver fibrosis
15 year survival is 70%
CYSTIC RENAL DYSPLASIA
Abnormality of embryologic differentiation characterized by ABNORMAL STRUCTURES in the kidney and ABNORMAL LOBAR ORGANIZATION –> kidney very DEFORMED, UNRECOGNIZABLE; cysts contain shit that doesn’t belong in kidney (cartilage!), may be unilateral or bilateral
Presence of IMMATURE COLLECTING DUCTS and CARTILAGE (mesenchymal elements)
Presents as SUBTOTAL or TOTAL
Sub = non-evident and may be inadvertently discovered
Total = BILATERAL = INCOMPATIBLE WITH LIFE!
Cysts in general
Develop as we age - about half of autopsies for those over 50 have renal cysts
Simple cysts = thin, smooth walled, filled with clear fluid
Complicated cysts = thick walled, filled with debris or hemorrhage and are associated with masses –> need investigation
