Kidney Anatomy and Nephron Function

• The kidneys consist of two main regions: the outer renal cortex and the inner renal medulla, which house nephrons.
• Kidney disease involves structural damage (e.g., glomerular injury, tubulointerstitial fibrosis), which impairs the kidney's ability to filter blood, leading to waste accumulation.
• Symptoms such as flank pain, edema, hypertension, and renal failure may indicate structural kidney issues.

Segments of the Nephron Tubules and Primary Functions

• Proximal Convoluted Tubule (PCT) reabsorbs most filtered water, electrolytes, and glucose.
  • Damage to the PCT causes impaired reabsorption, leading to electrolyte imbalances and dehydration.
• The Loop of Henle creates a concentration gradient essential for water reabsorption.
  • Disruption leads to problems concentrating urine and imbalanced fluid status.
• Distal Convoluted Tubule (DCT) facilitates sodium reabsorption and potassium secretion under aldosterone influence.
  • Dysfunction results in electrolyte disturbances, especially affecting potassium levels.
• Collecting Duct is the final site for water reabsorption, influenced by ADH.
  • Damage to the collecting duct leads to polyuria or oliguria depending on ADH regulation.

Normal Functions of the Kidneys

• The kidneys filter blood, regulate fluid and electrolyte balance, and excrete waste products like urea and creatinine.
• The kidneys regulate blood pressure through the renin-angiotensin-aldosterone system (RAAS).
• The kidneys produce erythropoietin for red blood cell production.
• Kidney dysfunction arises from factors like diabetes, hypertension, infections, or autoimmune diseases, leading to fluid retention, electrolyte imbalance, or failure to excrete toxins.
• Impaired kidney function produces symptoms like swelling, high blood pressure, fatigue, and confusion.

Characteristics of Normal Urine

• Normal urine is clear, light yellow, contains minimal protein and glucose, and no blood.
• Deviations from normal urine characteristics can occur due to underlying renal or systemic issues like infections or metabolic disorders.
• Dark or cloudy urine, hematuria, or foul-smelling urine indicate infection or kidney pathology.

Specific Gravity, BUN, Creatinine, GFR

• Specific gravity, BUN, creatinine, and GFR are key indicators of kidney function.
  • Specific Gravity measures urine concentration and normally ranges between 1.010 and 1.030; abnormalities may indicate dehydration or renal disease.
  • Blood Urea Nitrogen (BUN) reflects kidney filtration; elevated levels indicate kidney dysfunction or dehydration.
  • Creatinine, a byproduct of muscle metabolism, marks kidney function; elevated levels denote renal impairment.
  • Glomerular Filtration Rate (GFR) measures kidney filtering capacity, with a decrease indicating impaired function.
• Changes in specific gravity, BUN, creatinine, and GFR signal acute or chronic kidney disease, dehydration, or glomerular injury.

Kidney Stones

• Stones form from crystallized substances like calcium, oxalate, or uric acid in the kidneys.
• Risk factors include dehydration, high-sodium or high-oxalate diets, genetic predisposition, and certain medical conditions (e.g., gout).
• Types of stones include those made of calcium oxalate, uric acid, struvite, and cystine.
• Manifestations include severe flank pain, hematuria, nausea, vomiting, and painful urination.

Causes of Urinary Tract Obstructions

• Obstructions block the normal flow of urine, leading to pressure buildup, possible infection, and kidney damage.
• Causes include kidney stones, tumors, enlarged prostate, or congenital abnormalities.
• Symptoms include painful urination, frequent urge to urinate, hematuria, and possible urinary retention.

Cystitis

• Cystitis involves inflammation of the bladder, often due to bacterial infection.
• The most common cause is E. coli from the gastrointestinal tract, but viruses or fungi can also cause it.
• Manifestations are frequent, painful urination, lower abdominal discomfort, and cloudy, foul-smelling of urine.

Pyelonephritis

• Pyelonephritis is a kidney infection, usually ascending from the bladder, causing inflammation and possible kidney damage.
• Often caused by E. coli, with risk factors including urinary tract obstruction, pregnancy, or diabetes.
• Symptoms exhibited are fever, flank pain, dysuria, nausea, and vomiting.

Protective Mechanisms to Decrease UTI

• Normal urinary tract mechanisms include acidification of urine, mucosal immunity, and efficient urine flow to prevent infection.
• UTI risk increases when these mechanisms are compromised by factors like obstruction, poor hygiene, or weakened immune systems.
• Infections produce symptoms like pain during urination, urgency, and frequent urination.

Glomerulonephritis

• Inflammation of the glomeruli impairs filtration.
• Nephrotic syndrome leads to significant protein loss, edema, hyperlipidemia, and hypoalbuminemia.
  • Often caused by infections, autoimmune diseases, or systemic conditions like diabetes.
  • Symptoms are swelling (especially in the legs and around the eyes), foamy urine, and weight gain.
• Nephritic syndrome results in hematuria, hypertension, and oliguria.
  • Commonly caused by post-streptococcal infection.
  • Manifestations involve blood in the urine, decreased urine output, and high blood pressure.

Acute Tubular Necrosis

• Damage to the tubules of the kidneys is typically due to ischemia or nephrotoxins.
• Causes include prolonged hypotension, certain medications (e.g., NSAIDs, antibiotics), or toxins.
• Manifestations of acute tubular necrosis are oliguria, increased creatinine, and electrolyte imbalances (hyperkalemia, acidosis).

Acute Renal Failure

• Acute Renal Failure features a rapid decline in kidney function that leads to the retention of waste products.
  • Phases include initiation (the onset of injury), oliguria (reduced urine output and increased serum creatinine), diuretic (increased urine output as kidneys recover), and recovery (gradual improvement in kidney function).
• Diagnosis involves blood tests (e.g., creatinine, BUN), urine output measurement, and imaging studies.
• Etiology encompasses ischemia, nephrotoxins, infections, or obstruction.
• Symptoms experienced are decreased urine output, swelling, confusion, fatigue, and nausea.

Chronic Renal Failure

• Chronic Renal Failure is marked by a gradual loss of kidney function over months to years.
• Typical causes are diabetes mellitus, hypertension, and glomerulonephritis.
• Presenting signs may be fatigue, swollen ankles, high blood pressure, and uremic symptoms (itching, nausea).

Neurological Control of Bladder Function

• Bladder control is mediated by the autonomic nervous system: parasympathetic (for bladder contraction) and sympathetic (for bladder relaxation) systems.
• Nerve pathway disruptions (e.g., spinal cord injury, neurological diseases) impair bladder control.
• Manifestations include involuntary urination, difficulty emptying the bladder, or inability to initiate urination.

Types of Incontinence

• Stress Incontinence involves leakage due to increased intra-abdominal pressure (e.g., coughing, sneezing).
• Urge Incontinence is marked by a sudden, intense urge to urinate with involuntary leakage.
• Overflow Incontinence results from involuntary leakage due to bladder overfilling.
• Functional Incontinence involves the inability to reach the toilet in time because of physical or cognitive limitations.

Neurogenic Bladder

• Nerve damage affects bladder control, leading to problems with voiding or retaining urine.
• Etiology often consists of spinal cord injuries, multiple sclerosis, stroke, or diabetes.
• Manifestations include difficulty initiating urination, incomplete emptying, urinary retention, or incontinence.

The kidneys consist of the renal cortex and medulla, housing nephrons. Kidney disease involves structural damage, impairing blood filtration. Nephron tubules are the proximal convoluted tubule, loop of Henle, and distal convoluted tubule. Each segment plays a vital role in reabsorption and secretion.