Patho Week #8: Renal and Urinary Function

1. Filtration and removal of nitrogenous wastes in the form of urea and other waste products
2. Maintenance of homeostasis, including fluid and electrolyte balance and acid/base balance
3. Maintenance of BP through Baroreceptroes in the juxtaglomerular apparatus, which sense the blood pressure/ fluid flow and release the appropriate amount of renin

4. Synthesis, regulation and activation of hormones
a. Erythropoietin: Stimulates blood growth
b. Renin: Renin-Angiotenstion-Aldosterone system, and BP
c. Calcitonin: Activated form of Vitamin D, which promotes calcium absorption in intestines and reabsorbtion of phosphate in the kidneys

*Beings in Glomerulus, where blood moves through to the bowmans capsule
*The amount that is filtered here is known as Glomerulur Filtration Rate (GFR), and is primary way to assess kidney function
*When there is strong vasoconstriction, (Sepsis or shock) the golmerular arteries can constrict so much that no urine is formed

*Onces the filtrate passes from the golmerulus to the bowman capsule, it then moves to the proximal tubule.
*Reabsorbtion or further secretion from the BV can occur in proximal tubule
*H20 and Urea are passively transported
*Elctrolytes, Glucose, Urate and Amino Acids require active transport

*Controlled by 3 mechanisms:
a. ADH: Works in collecting tubule causing H20 to be absorbed back into circulation and the urine to be more concentrated
b. Level of Vasoconstriction: (The greater the VC, the less filtration, AKA more concentrated)
c. Osmolality (Concentration) of the Blood

*Regulates and maintains water fluid balance

*Filtration of plasma per unit of time which is directly related to renal blood flow
*Normal eGFR >90
*Mild Impairment eGFR 60-89
*Moderate Impairment eGFR 30-59
*Severe Impairment eGFR 15-29
*Failure eGFR <15
*We consider anything >60 to be normal

*We dont use this on its own bc it can greatly underestimate kidney damage, especially in those who are older or have low body weight
*Male: .6-1.5 mg/dl
*Femaile: .6-1.1 mg/dl

*Measures the amount of urea in blood
*If it is high it is an indication that not enough urea is being filtered by the kidneys
*Normal: 7-18 mg/dl

*Measures elctrolytes, calcium, phosphate, pH and C02

A. Specific Gravity: Hydration Level
B. Glucose: Increased with DM
C. Ketones: + w diabetic ketoacidosis, starvation or low carb intake
D. Blood: + w bleeding in UT or kidney
E. Leukocyte Esterase: + w UTI or kidney infection
F. Nitrate: + w UTI or kidney infection
G. Bilirubin: + w liver failure/disease
H. Urobilinogen: + w live cirrhosis, hemolytic anemia or hepatic or biliary obstruction

*Collected from a urine sample
*Used to determine potential for kidney damage due to microvascular effects of DM

*Blockage of urine flow within the urinary tract
*Can be caused by anatomic or functional defect that leads to urinary stasis, dilates the urinary system, increase risk for infection and compromised urinary function

*Masses of crystals, proteins or other substances that form within and may obstruct the UT
*Risk Factors: Gender, race, geographic location, seasonal, fluid intake, diet and occupation
*Pathophysiology: Super saturation of one or more salt substances. There is a higher salt concentration than the volume able to dissolve it. Salt goes from liquid to solid and grows with crystallization or aggregation

*Calcium oxalate or calcium phosphate
*Caused by hypercalcemia, generally due to hyperthryoidisim, vitamin D overdose, bone disease or internal bypass surgery
*Treat the underlying cause, restrict foods high in oxalate (Beer, berries, grapes, cucumbers, PB etc.) and hydrate

*Magnesium ammonium phosphate
*Generally caused by UTI
*Treat the infection and increase fluid intake

*Formed when urine is acidic, or by gout, or high purine diet
*Treat with increased fluid intake and treat underlying condition

*Inherited genetic disorder of amino acid metabolism
*Treat with increased fluid intake and make urine more alkaline

*Flank Pain
*Hydration often makes the pain worse bc it increases the pressure on the stone
*Need to give hydration, after the stone has passed

*Urinalysis: Will often show blood, pH abnormalites, which can help to differentiate between the stones
*Kidney, Ureter, Bladder (KUB) X-ray: Can show most stones
*Intravenous Pyelogram (IVP)
*Abdominal CT:
*Stone Analysis: Used to determine cause to prevent future stones

*Removal of Stones
*Stones less the 5mm can pass on their own
*Stone greater the 5mm we use shock waves to crush them using an ultrasound or they are surgically removed

*Hydronephrosis: Obstruction causes buildup of fluid in the kidney and if not treated soon enough it can lead to kidney failure
*Pyelonephritis: Kidney Infection

*Inflammation of the urinary epithelium following invasion and colonization by some pathogen within in the UT
*Women have a great risk
*Common Pathogens:
a. Eschericia Coli (80%)
b. Staphylococcus Saprophyticus
c. Enterobacter

*UTI can cause Cysitis, an inflammation of the bladder.
(Cystitis can also be caused by trauma, autoimmune or from medications)
*Manifestations: Frequency, dysuria (painful urination), urgency, lower abdominal pain/ superpubic pain. Elderly will often present with delirium
*Treatments: Antimicrobial therapy, and increased fluid intake. Cranberry pills have shown to reduce risk in those with chronic infection bc is has a consistent hydration

*Can come from a UTI or on its own

*Acute infection of the ureter, renal pelvis and/or renal parenchyma
*Manifestations: Rapid onset of fever, chills, malaise and flank pain. Elderly will appear more symptomatic then with a UTI
*Treated with antibiotics for 10-14 days
*Can lead to kidney nephron scarring, which can caused end stage renal failure

*Persistent or recurring episodes of acute pyelonephritis
*Risk of chronic pyelonephritis increases in ppl with renal infections and other obstructive pathological conditions
*Can lead to loss of tubular function and ability to concentrate urine
*Leads to Polyuria (Peeing a lot), Nocturia (Peeing at night) and Proteinuria (Increase protein in urine)
*10-20% of cases lead to end stage renal failure

*Golmerulur disease demonstrates a sudden or insidious onset of hypertension and edema
*Severe cases can lead to acute renal failure

*Decreased GFR Rate: Golmerulur damage causes a decreased golmerulur capillary blood flow
*Elevated Plasma Creatinine, and BUN Levels
*Decreased Creatinine Clearance
*Increased golmerulur capillary permeability and loss of plasma proteins into the urine resulting in Hypoalbuminemia

*Inflammation of the glomerulus
*Causes: Immunologic abnormalities, drugs/toxins, vascular/systemic disorders (Lupus), viral, post-infection inflammation or sepsis
*Most commonly due to inflammation after a kidney infection due to WBC infiltration
*Generally occurs 7-12 after infection

*Deposition of cirucaltion soluble antigen-antibody complezes, often with complement fragments
*Formation of antibodies against the glomerulur basement membrane
*Streptoccocal release of neuramidase

*Hematuria: Cola-Colored Urine, from blood
*Oliguria: 50-400cc per 24hrs (Low output)
*Edema: Around eyes, feet and ankles
*Hypertension
*Decreased GFR

*Antibiotics for infection
*Minimizing the immune response
*Symptomatic management

*Causes:
a. Decreased Blood Volume
b. Ischemia
c. Toxic Injury
d. Obstructive Injury
*Mortality rate of 40-75%, not bc of the renal failure itself but it is generally a symptom of a worse problem such as trauma, shock or sepsis

*Most common cause of ARF
*Caused by decreased blood flow to the kidney bc of hemmoraging, severe hydration, contrast dye, medications, impaired perfusion due to HF or shock, sepsis or anaphylaxis
*Elderly are at a high risk bc of higher prevelance of renal-vascular disorders and hypovelmia (Blood Loss)
*Manifestations: Elevated BUN:CR >20:1, elevation of urine osmolality >500, and hyaline casts

*Caused by damage to strucutres within the kidneys
*Often caused by prerenal conditions such as ischemia or medication toxicity. Can also be caused by acute glomerulurnephritis or pyelonephritis
*Most common cause is Acute Tubular Necrosis (ATN), which is where epithelial cells in the tubules are destroyed from ischemia, sepsis, infection or obstruction. Generally it is reversible
*Manifestations: BUN:CR is < 20:1, granular casts or renal tubular casts

*Caused by obstruction from stones, tumors, strucutres of the urethra or ureters, or BPH
*Obstruction leads to hydronephrosis and then if not reveresed, the nephrons become damaged and destresed which leads to ARF
*If too many nephrons are damaged before it is reverse, it can caused Chronic Renal Failure
*Manifestations: BUN:CR is >20:1, and urine osmolality is low, 400, meaning the urine is dilute

*N/V
*Malaise
*Altereted senses
*Diffused abdominal or flank pain
*Generalized edema
*Oliguira (Low urine output) or Anuria (No urine output)

*CVVH (Hemofiltriation): Continuous, low volume dialysis
*Hemodialysis: Periodic, high volume dialysis
*Correct underlying cause if possible

*Occurs when the kidney is no longer able to effectively maintain homeostasis and remove wastes
*Causes: ARF, diabetes, hypertension, glomerulonephritis, systemic lupus erythematous or polycystic kidney disease (ADD, multiple cysts on both kidneys)

*Staged using GFR
*Stage 3: (Moderate) GFR 30-59, only treat complications and attempt to prevent further disease by treating underlying condition (HTN, DM)
*Stage 4: (Severe) GFR 15-29, start dietary restriction on water, K, phosphate, protein, and magnesium. Additional meds necessary
*Stage 5: (Kidney Failure) GFR <15, requires dialysis, also known as End Stage Renal Failure

*Hypertension: Due to NA/H20 imbalance, can lead to CHF
*Hyperkalemia: Increase Potassium
*Uremia: High serum urea, can lead to coagulopathies (Bleeding Disorders)
*Anemia: Due to reduced erythropoitein production

*Metabolic Acidodsis
*Hypocalcemia: Due to Vitamin D not being activated. (Can lead to hyperthryodisim and bone disease)
*Hyperphosphatemia: (Can lead to hyperthryodisim and bone disease)
*Encephalitis: Due to uremia, at the very end stage

*Hemodialysis: 3-4/wk, Blood flows from the pt into the machine, and cleans the blood and returns to homeostasis
*Peritoneal Dialysis: Preformed at home, multiple times a day and fluid is placed into the peritoneal space through a shunt and then removed with urea and other wastes
*Diet Modification: Reduction in H20, NA, K, Phosphoros, Magnesium and Protein
*Medications that are really cleared need to be adjusted depending on their role and function
*Kidney Transplant