Kidneys since are involved in the crucial aspect of detoxification, become susceptible to
multiple adverse conditions, that affect their overall functioning. Imagine these vital organs
getting abnormally enlarged due to development of fluid-filled cysts numbering in thousands,
compressing the healthy tissue and hampering kidney function eventually causing renal failure!
Such is the havoc unleashed by an inherited kidney disorder belonging to the family of cystic
kidney diseases; Polycystic kidney disease (PKD). A medical condition characterised by growth
of multiple cysts which are abnormal fluid-filled sacs with an unknown complex protein
constituency of cyst fluid, arising out of the tubular portion of nephrons as well as the renal
collecting system. A very conservative estimate states about, 650,000 to 2,200,000 individuals
develop end-stage renal diseases in India annually, while 2.4% cases of the end stage disease
is solely contributed by Polycystic kidney disease.
Types of Polycystic kidney disease and Causes
The major causal factor of Polycystic kidney disease is inherited gene defects, and rarely occurs due to spontaneous
genetic alterations. This is mainly categorised into two main types:
Autosomal Dominant PKD (ADPKD): Accounting for almost 90% of the Polycystic kidney disease cases (affects 1 in 800),
it is also termed the 'adult PKD. This condition is characterised as a progressive and a multi-systemic
disorder resulting in bilateral renal enlargement due to the development of fluidfilled cysts on the
kidney and later in other organs like liver, spleen, pancreas, etc. Mutations in a set of genes PKDI
(16p13.3) and PKD2 (4q21-23), encoding for the two integral membrane proteins localised in the
renal cilia: polycystin-1 and polycystin-2, respectively, are documented to be responsible for
development of ADPKD.
ADPKD caused due to mutation in either of the genes causes similar clinical manifestation,
although patients harbou ring mutations in Polycystic kidney disease/ are affected by kidney failure and other
clinical symptoms quite early.
Signs and symptoms: It is usually diagnosed in the fourth
decade of life (30s-40s) until the cysts are half an inch or larger i.e. first growing out of
the nephrons, later separating out upon enlargement. Depending on its severity, initially
ADPKD affected complain of hypertension, temporary or persistent pain in the back and
sides, ribs and hips, abdominal pain, headaches, etc., and hematuria (presence of blood
in urine).
Future Complications: Infiltration of functional parenchyma with monocytes and
fibroblasts results in renal fibrosis due to secondary and tertiary changes induced by
the expanding fluid-filled cysts ultimately causing renal failure. Few other conditions
like infection in the cyst, urinary tract infections (UTIS), development of Kidney stones,
cerebral aneurysms, etc. are observed in ADPKD
patients, which worsen their condition, and the existing damage.
Autosomal Recessive PKD (ARPKD): This is a rare genetic disorder occurring in 1
in 6000 to 1 in 40,000 live births, often termed as 'infantile PKD', appears in the
early months of life, afflicting neonates or even fetuses in the womb. Since it is an
autosomal recessive disorder, there are 25% chances of inheritance in case both the
parents carry a copy of the mutated gene.
ARPKD is a combination of renal cystic
disease and congenital hepatic fibrosis. Epithelial hyperplasia along the collecting
ducts and fluid secretion results in ductal ectasia, thereby causing renal dysfunction.
Clinical presentation with the age of onset of ARPKD is variable and is governed by
differential expression of mutations in PHKD1 along with a role of modifier genes
and environmental factors, and is further classified as:
- Perinatal ARPKD (Present at birth)
- Neonatal ARPKD (Within the first month of life)
- Infantile ARPKD (3-6 months old)
- Juvenile ARPKD(>1 year old)
Signs and symptoms
- Enlarged kidney of fetus or an infant upon ultrasound
- Reduced amniotic fluid surrounding the baby in uterus
- Potter's syndrome (deformity in face, ears and limbs due to lack of amniotic fluid)
- Enlargement of child's abdomen due to enlarged kidneys, liver or spleen
- Growth failure: Affected kids are smaller than average size
- Heart defects
- Underdeveloped lungs
- Frequent urination
Future Complications: In severe cases of ARPKD, babies die at birth or within the first few
weeks of life due to pulmonary insufficiency. The ones which survive till adolescence suffer
from high blood pressure leading to cardiovascular problems, UTIs, low blood cell counts,
varicose veins, hemorrhoids, liver scarring, etc. and eventually develop kidney failure before
reaching adulthood.
Acquired Cystic Kidney Disease (ACKD): As the name suggests is not inherited
but develops in patients affected by other pre-existing adverse kidney conditions. It usually occurs
at a later stage in life especially in individuals under dialysis or those affected by kidney failure.
Diagnosis
Doctors perform differential diagnoses to eliminate other possible causes like ACKD,
medullary cystic disease, etc. Hypertension and rise in diastolic blood pressure are few
of the initial manifestations of ADPKD along with abdominal tenderness over the liver
and heart murmurs, to name a few. A doctor analyses for these existing symptoms along
with recording prior medical history of the patient and the family. In case of suspected
ADPKD, the following kidney studies are recommended to be performed:
Kidney Function Tests:
The glomerular filtration rate (eGFR) test is the most
recommended as it is considered to be the best to measure rate of kidney
function as well as assess stage of kidney disease. It measures the rate at which kidneys
filter blood and is calculated using a mathematical formula involving age, gender, etc. to
the patients creatinine levels. Values of less than 60mL/min/1.73m" indicate a diseased
kidney. A simple urine test is also done to check for early signs of Polycystic kidney disease, viz. presence of
blood or protein (albumin).
Ultrasonography:
Abdominal ultrasound, one of the initial tests performed for suspected
ADPKD, provides accurate images of cysts in the kidneys (1-1.5 cm) as well as the extrarenal
features of ADPKD like pancreatic and hepatic cysts, etc. in adults. In case of unborn fetuses,
it is recommended when enlarged and echogenic kidneys are highlighted during routine
obstetric sonogram (suspected ARPKD). Ultrasound scans can also evaluate abdominal
masses or renal insufficiency in newborns and portal hypertension in an older child, whereas
doppler ultrasonography evaluates blood flow.
Computed Tomography (CT) Scan:
A sensitive platform, CT scan utilises thin X-ray beams
that can detect cysts as small as 0.5 cm and produce precise images of kidney cysts as fairly
well-defined, round or oval masses along with renal calculi and acute or spontaneous hemorrhage
into a cyst in ADPKD patients. ARPKD affected undergo CT scan which effectively demonstrates
nephromegaly, hepatic duct dilation, varices and splenomegaly. One should however take into
consideration nephrotoxicity of intravenous CT contrast material in patients with renal failure.
Magnetic Resonance Imaging (MRI) Scan:
This imaging technique is recommended in patients especially if they have an allergy for iodinated
contrast media and those affected by renal failure. This can distinguish renal cell carcinoma from
simple cysts and aids in monitoring cyst growth as well, to asses disease prognosis in adults.
Fetal MRI scans characterise the findings of ARPKD in utero highlighting nephromegaly with
reniform-shaped kidneys along with other features like fluid-filled, ectatic collecting ducts.
Genetic testing:
This is not routinely performed but is recommended in
individuals with suspected ADPKD with a prior family history of the same. Testing for genetic
mutations in PKD1 or PKD2 may be done using the blood or saliva sample. However, considering
the complexity of the test procedure, reporting may take up to a month. In case of a positive
mutation, further analysis by a genetic counsellor is recommended.
Cerebral angiography to identify cerebral aneurysms and Intravenous pyelogram are other
X-ray imaging modalities performed for monitoring Polycystic kidney disease prognosis.
Treatment and Management
There is no cure or prevention modality available for Polycystic kidney disease and hence treatment focuses on
controlling symptoms like high blood pressure, UTIs, pain, etc. by medications and preventing
future complications. Up to 50% of ADPKD patients undergo renal replacement therapy or kidney
transplantation by 60 years of age whereas ARPKD affected may undergo peritoneal dialysis or
combined liver and kidney transplantation depending on the age of onset. Surgical drainage of
renal and hepatic cysts is also performed when conventional antibiotic therapy fails.
A PKD affected should undergo lifetime monitoring by an experienced dietitian and must adhere
to the following strategies to mittigate the same .
- Abstain from alcohol and smoke, and adhere to a
healthy lifestyle with diet rich in nutrients, protein,
and fiber
- Follow a low-salt, low-fat and cholesterol, low sugar
diet regimen
- Maintain a healthy body weight by performing daily moderate physical
activity for at least 30 minutes
- Regular intake of medications as directed by the doctor .
Kidney health is often underrated and Polycystic kidney disease affected are chronic ill patients, who shouldn't
be let to deal with the illness alone. Polycystic kidney disease risk is serious, if caught early; its progress can be
impeded or stopped, only if one is proactive enough to heed to the symptoms manifested
in the first few months of life or later.
