Author Question: Fred, a fit and healthy 44-year-old, was working outside one warm summer afternoon. When he returned ... (Read 26 times)

joesmith1212 · **on:** Jun 25, 2018

Fred, a fit and healthy 44-year-old, was working outside one warm summer afternoon. When he returned home by the end of the day, his lower back felt sore and he felt nauseated. His wife made him dinner, but he was not hungry and chose to go to bed instead

Fred's symptoms progressed, and soon he was rolling on the bed with excruciating pain. He said his back hurt as well as his stomach and groin area. The pain would ease off only to return a short while later, and when it did, Fred would begin to sweat and run to the bathroom to vomit. His wife became concerned and started the car. When his symptoms abated, she helped him into the car and rushed him to the hospital.

At the hospital, an abdominal radiograph showed the presence of renal calculi in Fred's right ureter (urolithiasis). What is the mechanism of stone formation in the kidney? What is the role of citrate in the kidneys?

Why would the administration of calcium supplements be useful for a patient with calcium oxalate stones?

Hydronephrosis can be a complication of renal calculi. What is hydronephrosis? How does back pressure occur in a kidney, and what physiological mechanism is responsible for nephron damage when back pressure is present?

Question 2

Will is a 68-year-old male with a history of hypertension. Eight months ago, he started regular dialysis therapy for ESRD. Before that, his physician was closely monitoring his condition because he had polyuria and nocturia.

Soon it became difficult to manage his hypertension. He also lost his appetite, became weak, easily fatigued, and had edema around his ankles. Will debated with his physician about starting dialysis, but she insisted, before the signs and symptoms of uremia increased, the treatment was absolutely necessary.

What is the difference between azotemia and uremia?

Two years ago, Will's physician told him to decrease his protein intake. In spite of what the physician ordered, Will could not stop having chicken, beef, pork, or eggs at least once a day. Why did his physician warn him about his diet?

Will's feelings of weakness and fatigue are symptoms of anemia. Why is he anemic?

Knowing what you do about Will's history, why is left ventricular dysfunction a concern for his physician?

olderstudent · **Reply #1 on:** Jun 25, 2018

Answer to Question 1

The formation of renal calculi relies on supersaturated urine, a nidus, and a deficit in stone inhibitors. Calculi are formed from particular crystals that are not unbound and highly concentrated in the urine. These components aggregate around a small nucleus of organic or inorganic material that acts as an attracting force for stone formation. The presence of a nidus lowers the level of supersaturation normally needed for the development of calculi. Citrate, along with magnesium and the Tamm-Horsfall mucoprotein, acts to inhibit stone formation. Citrate is administered clinically as a means to prevent the formation of hypocitraturic calculi.

Calcium supplementation encourages the binding of oxalate to calcium in the gut. The oxalate fails to be absorbed into the bloodstream and is subsequently excreted.

Hydronephrosis occurs when an obstruction causes urine to accumulate in and dilate the renal pelvis and calices. Back pressure occurs in the kidney when glomerular filtration is still occurring, yet formed urine is unable to leave the kidney due to an obstruction. Nephrons suffer mechanical damage from the increased intrapelvic pressure and ischemic damage from alterations in blood flow.

Answer to Question 2

Both azotemia and uremia describe the accumulation of metabolic wastes (normally excreted as urine) in the blood. Azotemia is the presence of nitrogenous wastes (urea, uric acid, and creatinine) in the blood and is often asymptomatic. Uremia results when all the products of urine accumulate in the blood and cause systemic manifestations. Uremia includes acid-base, electrolyte, and fluid imbalances. Without treatment, uremia results in multiorgan failure, coma, and death.

In renal sufficiency, the kidneys have difficulty in secreting the waste products of protein metabolism. A low-protein diet during this time can slow the progression of renal failure and decrease the symptoms of uremia.

In renal failure, erythropoietin secretion declines and red blood cell production falls below the needs of the body. The life span of RBCs is also shortened due accumulation of nitrogenous waste. Finally, if Will's anorexia was significant, a deficiency in dietary iron would also be a factor in the development of his anemic state.

Hypertension increases workload on the left ventricle and increases oxygen demand. Anemia contributes to left ventricular hypertrophy and ischemic events. Together, coupled with extracellular fluid overload, are all factors in Will's history that predispose him to left ventricular dysfunction or congestive heart failure.