The pathogenisis of PKD have not attained consensus up to now. Some researchers thought Polycystic Kidney may result from the expansion of Bowman cyst, or it may be aroused by the expansion of convoluted tubule. It is caused by the connecting obstruction between glomerulus, convoluted tubule and collecting tubule developed from Wolffian tubule.
Bialestack pointed that some cysts are abnormal hyperplasia nephrons, which
is called huge nephrons. Still some other people regard that some cysts have a
function of excreting.
Bricker has made chemical analysis on cyst liquid, and the finding shows that
the component of it liquid is similar to that of urine.
Norris thought that many temporary nephrons units can not shrink normally and
some nephrons present local coarctation and segmentation. Therefore, cysts with
different sizes occur. Hepler assumed that this disease happens because renal
blood circulation has abnormal distribution, which results in the regression of
Hidd-brant proposed that the connection was lost between secretion organ and
excretion organ during the growing period. And secretion organ is blocked and
secretion can not be discharged. Then cysts appear.
Still other people thought that fibrous obstructions were caused in excretion
pipe by mechanical factor, say, local infection in fetus stage, or urinary
cylinder or undissolved calcium salt, which obstruct urine excretion, arousing
enlargement to the renal tubule gradually.
There are still two views which can explain some clinical symptoms:
Dammin regards that gland system have excessive gland tubule epithelial cell
formation during the development of normal embryo. But epithelial cell of the
gland system can degenerate, and disappear in the ensuing development stage. In
the beginning of degeneration, these epithelial cells finish the segmentation of
epithelial tubule. If segmentation does not degenerate, cysts can appear, which
can explain the phenomenon than multiple cysts occur in spleen, pancreas, or
even ovary, womb and bladder.
This disease is usually related with bilateral kidneys. The weight of a
normal kidney is about 150g. As for ADPKD patients without symptoms, single
kidney weighs 256g on average and this number may be 465g on average if patients
have symptoms. It is common to see diffusive cysts among kidneys of ADPKD
Cysts with different sizes distribute in renal cortex and medulla
fully, which make kidney seems like a string of grapes. Epithelial cells on cyst
wall have limited hyperplasia, forming polyp-like shape. Besides, ECM has
abnormal hyperplasia, and proximal tubule expands and develops into cyst in
which the component of fluid is similar to plasma. Cyst developed from distal
tubule, with less sodium and chlorine but higher urea and creatinine in the cyst
liquid. With age growing, the number of cyst increases and cystic cavity enlarge
to 2-3cm in diameter for patients with symptoms. In the final stage, cyst
diameter can reach 20-30cm and the total kidneys are occupied by cyst virtually.
Generally, cysts with more than 3cm diameter usually contain fluid similar to
blood or blood clot.
Polycystic Kidney section presents that cysts are located in renal cortex and
renal medulla in conformity and kidney pelvis and kidney calices change their
normal shape obviously. In severe cases, there is seldom remaining renal tissue
virtually. As for patients with lighter symptoms, this disease is usually
confused with multiple simple cyst disease.
It can be observed under microscope that normal renal tissue is pressed by
neighboring cysts. Based on the Angiosclerosis or Pyelonephritis, glomerulus
sclerosis, tubule shrink and mesenchyme fibrosis develops. It's difficult to
identify cysts tissues' resource, unless cyst keeps its original tissue in
normal position and morphological features of epithelial cells.
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