Is there a connection between kidney function and dairy products (or
other high phosphorus foods) such that a person might present with
pruritis (mainly, itchy skin rashes); and, if so, why is this so? 
What's the relationship/connection?

Hello -

Hyperphosphatemia (elevated phosphate in the blood) is most commonly
the result of kidney dysfunction.  Phosphate is eliminated from the
body through the kidneys, and if they are not functioning properly,
phosphate will accumulate in the body.  Most of the time,
hyperphosphatemia is asymptomatic, however, it can cause various
symptoms including 1) muscle cramps, 2) tetany, and 3) perioral
numbness or tingling, 4) bone and joint pain, 5) pruritus, or 6) skin
rashes.  Most of the symptoms of hyperphosphatemia (1-4) result from
hypocalcemia (elevated levels of phosphate lead to low levels of
calcium in the body).  Other symptoms (5-6) may exist on their own, or
may be exacerbated by other compounds that are not eliminated from the
body due to kidney dysfunction.

Dairy products, as you note, are high in phosphorous content and it is
commonly recommended for individuals with hyperphosphatemia to
eliminate dairy products from their diets.  Phosphorous content of
foods correlates well with protein content - restriction of the amount
of protein ingested is also sometimes recommended to reduce
phosphorous intake in individuals with difficult to control
hyperphosphatemia.

If dietary control is either not feasible or fails, phosphate binding
compounds can be given to help the individual excrete more
phosphorous, thus lowering their blood levels of phosphorous. 
Aluminum or magnesium containing antacids are amoung the cheapest used
compounds.

Phosphorous may produce pruitis by exacerbating the effects of uremia
or by causing the precipitation of calcium in the skin - (calcium and
phosphate together form many hard crystalline forms, including tooth
and bone) - these areas of calcification can produce itching and
discomfort.


Please let me know if you have further questions or require
clarification.

synarchy

Recommendations for hemodialysis patients, including phosphorous
control:
http://www.ikidney.com/iKidney/Lifestyles/LifestyleTips/Hemodialysis/53TipsfortheHemodialysisPatient.htm

Definition of hyperphosphatemia (also references dairy ingestion and
kidney failure as common causes:
http://www.med.miami.edu/patients/glossary/art.asp?articlekey=3843

Recommendations for treatment from the National Kidney Foundation:
http://info.med.yale.edu/intmed/nephrol/pages/Divalent.html

A long article on hyperphosphatemia from eMedicine.com:
http://www.emedicine.com/med/topic1097.htm

Another long article, on renal failure, which discusses the elevation
of phosphorous seen, it's treatments, and side-effects, such as
pruritis:
http://cmbi.bjmu.edu.cn/heart973net/db-disease/Praxis%20Medicine%20-%20renal%20failure.files/cpmref.files/cpmref_main.htm

3 abstracts of articles researching the use of various phosphate
binders to help reduce phosphate levels in hyperphosphatemia:
http://www.ikidney.com/iKidney/InfoCenter/Library/JournalArticles/CalciumSalts.htm

search terms:
hyperphosphatemia, phosphorous, kidney, renal, pruritis

Although a bit brief, the answer was right on target.  And, the added
links for further reference were especially helpful.  Thanks...