Urinary Tract Obstruction

Overview

Epidemiology

• No specific epidemiological data
• More common than generally expected
• Rare cause of acute kidney injury Acute Kidney Injury Acute kidney injury refers to sudden and often reversible loss of renal function, which develops over days or weeks. Azotemia refers to elevated levels of nitrogen-containing substances in the blood that accompany AKI, which include BUN and creatinine. Acute Kidney Injury ( AKI AKI Acute kidney injury refers to sudden and often reversible loss of renal function, which develops over days or weeks. Azotemia refers to elevated levels of nitrogen-containing substances in the blood that accompany AKI, which include BUN and creatinine. Acute Kidney Injury)
• More common in children than adults, in patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship presenting with urinary tract Urinary tract The urinary tract is located in the abdomen and pelvis and consists of the kidneys, ureters, urinary bladder, and urethra. The structures permit the excretion of urine from the body. Urine flows from the kidneys through the ureters to the urinary bladder and out through the urethra. Urinary Tract: Anatomy symptoms or kidney failure (due to congenital Congenital Chorioretinitis abnormalities)
• More common in men than women (especially due to benign Benign Fibroadenoma prostatic hyperplasia Hyperplasia An increase in the number of cells in a tissue or organ without tumor formation. It differs from hypertrophy, which is an increase in bulk without an increase in the number of cells. Cellular Adaptation ( BPH BPH Benign prostatic hyperplasia (bph) is a condition indicating an increase in the number of stromal and epithelial cells within the prostate gland (transition zone). Benign prostatic hyperplasia is common in men > 50 years of age and may greatly affect their quality of life. Benign Prostatic Hyperplasia) as men age)
• More common cause of AKI AKI Acute kidney injury refers to sudden and often reversible loss of renal function, which develops over days or weeks. Azotemia refers to elevated levels of nitrogen-containing substances in the blood that accompany AKI, which include BUN and creatinine. Acute Kidney Injury in outpatient setting than in the hospital setting

Etiology

Etiology can be congenital Congenital Chorioretinitis, acquired, or functional. Urinary tract Urinary tract The urinary tract is located in the abdomen and pelvis and consists of the kidneys, ureters, urinary bladder, and urethra. The structures permit the excretion of urine from the body. Urine flows from the kidneys through the ureters to the urinary bladder and out through the urethra. Urinary Tract: Anatomy obstruction can occur anywhere along the urinary tract Urinary tract The urinary tract is located in the abdomen and pelvis and consists of the kidneys, ureters, urinary bladder, and urethra. The structures permit the excretion of urine from the body. Urine flows from the kidneys through the ureters to the urinary bladder and out through the urethra. Urinary Tract: Anatomy:

• Obstruction within the kidney causes dilation of specific affected calyces or caliectasis. 
• Obstruction at or distal to the renal pelvis Renal pelvis Kidneys: Anatomy causes diffuse caliectasis or hydronephrosis Hydronephrosis Hydronephrosis is dilation of the renal collecting system as a result of the obstruction of urine outflow. Hydronephrosis can be unilateral or bilateral. Nephrolithiasis is the most common cause of hydronephrosis in young adults, while prostatic hyperplasia and neoplasm are seen in older patients. Hydronephrosis.

Pathophysiology

• Obstruction induces apoptosis Apoptosis A regulated cell death mechanism characterized by distinctive morphologic changes in the nucleus and cytoplasm, including the endonucleolytic cleavage of genomic DNA, at regularly spaced, internucleosomal sites, I.e., DNA fragmentation. It is genetically-programmed and serves as a balance to mitosis in regulating the size of animal tissues and in mediating pathologic processes associated with tumor growth. Ischemic Cell Damage of the renal tubular cells: Glomerular cells are resistant to obstruction-related apoptosis Apoptosis A regulated cell death mechanism characterized by distinctive morphologic changes in the nucleus and cytoplasm, including the endonucleolytic cleavage of genomic DNA, at regularly spaced, internucleosomal sites, I.e., DNA fragmentation. It is genetically-programmed and serves as a balance to mitosis in regulating the size of animal tissues and in mediating pathologic processes associated with tumor growth. Ischemic Cell Damage. 
• Renal tubular cell apoptosis Apoptosis A regulated cell death mechanism characterized by distinctive morphologic changes in the nucleus and cytoplasm, including the endonucleolytic cleavage of genomic DNA, at regularly spaced, internucleosomal sites, I.e., DNA fragmentation. It is genetically-programmed and serves as a balance to mitosis in regulating the size of animal tissues and in mediating pathologic processes associated with tumor growth. Ischemic Cell Damage is mediated via caspases Caspases A family of intracellular cysteine endopeptidases that play a role in regulating inflammation and apoptosis. They specifically cleave peptides at a cysteine amino acid that follows an aspartic acid residue. Caspases are activated by proteolytic cleavage of a precursor form to yield large and small subunits that form the enzyme. Since the cleavage site within precursors matches the specificity of caspases, sequential activation of precursors by activated caspases can occur. Cell Injury and Death (generated from cytokine release Release Release of a virus from the host cell following virus assembly and maturation. Egress can occur by host cell lysis, exocytosis, or budding through the plasma membrane. Virology and inflammatory responses) 
• Prolonged obstructive processes induce tubulointerstitial fibrosis Fibrosis Any pathological condition where fibrous connective tissue invades any organ, usually as a consequence of inflammation or other injury. Bronchiolitis Obliterans and inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body’s defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation: accumulates extracellular matrix Extracellular matrix A meshwork-like substance found within the extracellular space and in association with the basement membrane of the cell surface. It promotes cellular proliferation and provides a supporting structure to which cells or cell lysates in culture dishes adhere. Hypertrophic and Keloid Scars and promotes fibrosis Fibrosis Any pathological condition where fibrous connective tissue invades any organ, usually as a consequence of inflammation or other injury. Bronchiolitis Obliterans 
• Postobstructive diuresis: 
  • Physiologic phenomenon seen after acute release Release Release of a virus from the host cell following virus assembly and maturation. Egress can occur by host cell lysis, exocytosis, or budding through the plasma membrane. Virology of bilateral obstruction 
  • Urine flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure increases by about 3–10-fold.
  • Possible mechanisms:
    • Impaired sodium reabsorption Sodium reabsorption Tubular System due to tubular damage 
    • Impaired urine-concentrating ability
    • Solute diuresis with excretion of retained urea Urea A compound formed in the liver from ammonia produced by the deamination of amino acids. It is the principal end product of protein catabolism and constitutes about one half of the total urinary solids. Urea Cycle 
    • Increased circulating natriuretic factor (ANP)

Clinical Presentation

Clinical presentation depends on the location, degree, and how quickly the obstruction develops.

Symptoms can include:

• Pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways:
  • Often absent
  • If present, is usually the result of bladder Bladder A musculomembranous sac along the urinary tract. Urine flows from the kidneys into the bladder via the ureters, and is held there until urination. Pyelonephritis and Perinephric Abscess distention, secondary infection, or obstructing stone/ mass Mass Three-dimensional lesion that occupies a space within the breast Imaging of the Breast
  • Associated with rate at which the distension develops
  • Often affects the flank or suprapubic region
• Change in urine output:
  • Azotemia Azotemia A biochemical abnormality referring to an elevation of blood urea nitrogen and creatinine. Azotemia can be produced by kidney diseases or other extrarenal disorders. When azotemia becomes associated with a constellation of clinical signs, it is termed uremia. Acute Kidney Injury
  • Polyuria Polyuria Urination of a large volume of urine with an increase in urinary frequency, commonly seen in diabetes. Renal Potassium Regulation
  • Nocturia Nocturia Frequent urination at night that interrupts sleep. It is often associated with outflow obstruction, diabetes mellitus, or bladder inflammation (cystitis). Diabetes Insipidus  
• Hypertension Hypertension Hypertension, or high blood pressure, is a common disease that manifests as elevated systemic arterial pressures. Hypertension is most often asymptomatic and is found incidentally as part of a routine physical examination or during triage for an unrelated medical encounter. Hypertension
• Hematuria Hematuria Presence of blood in the urine. Renal Cell Carcinoma

Classic laboratory findings:

• Elevated serum creatinine
• Urinalysis Urinalysis Examination of urine by chemical, physical, or microscopic means. Routine urinalysis usually includes performing chemical screening tests, determining specific gravity, observing any unusual color or odor, screening for bacteriuria, and examining the sediment microscopically. Urinary Tract Infections (UTIs) in Children with red cells or white cells 
• Hyperkalemic renal tubular acidosis Acidosis A pathologic condition of acid accumulation or depletion of base in the body. The two main types are respiratory acidosis and metabolic acidosis, due to metabolic acid build up. Respiratory Acidosis: 
  • Mostly found in patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship with chronic obstruction
  • Likely from mineralocorticoid resistance Resistance Physiologically, the opposition to flow of air caused by the forces of friction. As a part of pulmonary function testing, it is the ratio of driving pressure to the rate of air flow. Ventilation: Mechanics of Breathing impairing distal sodium reabsorption Sodium reabsorption Tubular System

Diagnosis

• Take a thorough history and physical:
  • Elicit any prior GU surgical history. 
  • Palpate for costovertebral angle tenderness. 
  • General abdominal exam assessing for suprapubic tenderness 
• Urinalysis Urinalysis Examination of urine by chemical, physical, or microscopic means. Routine urinalysis usually includes performing chemical screening tests, determining specific gravity, observing any unusual color or odor, screening for bacteriuria, and examining the sediment microscopically. Urinary Tract Infections (UTIs) in Children and culture: 
  • Hematuria Hematuria Presence of blood in the urine. Renal Cell Carcinoma: 
    • Gross 
    • Microscopic with > 3 RBCs RBCs Erythrocytes, or red blood cells (RBCs), are the most abundant cells in the blood. While erythrocytes in the fetus are initially produced in the yolk sac then the liver, the bone marrow eventually becomes the main site of production. Erythrocytes: Histology per high power field 
  • Pyuria Pyuria The presence of white blood cells (leukocytes) in the urine. It is often associated with bacterial infections of the urinary tract. Pyuria without bacteriuria can be caused by tuberculosis, stones, or cancer. Urinary Tract Infections (UTIs): WBCs in urine 
  • Bacteriuria Bacteriuria The presence of bacteria in the urine which is normally bacteria-free. These bacteria are from the urinary tract and are not contaminants of the surrounding tissues. Bacteriuria can be symptomatic or asymptomatic. Significant bacteriuria is an indicator of urinary tract infection. Urinary Tract Infections (UTIs) in Children: may reveal gross bacteria Bacteria Bacteria are prokaryotic single-celled microorganisms that are metabolically active and divide by binary fission. Some of these organisms play a significant role in the pathogenesis of diseases. Bacteriology in urine specimen 
• Labs: may reveal ↑ creatinine 
• Gold standard is imaging: 
  • Hallmark finding is dilatation of the collecting system in 1 or both kidneys Kidneys The kidneys are a pair of bean-shaped organs located retroperitoneally against the posterior wall of the abdomen on either side of the spine. As part of the urinary tract, the kidneys are responsible for blood filtration and excretion of water-soluble waste in the urine. Kidneys: Anatomy.
  • Ultrasound is the preferred imaging modality:
    • Advantage of no ionizing radiation Radiation Emission or propagation of acoustic waves (sound), electromagnetic energy waves (such as light; radio waves; gamma rays; or x-rays), or a stream of subatomic particles (such as electrons; neutrons; protons; or alpha particles). Osteosarcoma 
    • Inexpensive 
    • Identifies hydronephrosis Hydronephrosis Hydronephrosis is dilation of the renal collecting system as a result of the obstruction of urine outflow. Hydronephrosis can be unilateral or bilateral. Nephrolithiasis is the most common cause of hydronephrosis in young adults, while prostatic hyperplasia and neoplasm are seen in older patients. Hydronephrosis, but is not a functional test 
  • CT scan:
    • Provides superior anatomic information 
    • Ability to have contrasted images with both nephrographic and excretory phases 
    • Excretory phases allow for delayed contrast images to identify the level of obstruction 
    • Risks include: contrast nephropathy and ionizing radiation Radiation Emission or propagation of acoustic waves (sound), electromagnetic energy waves (such as light; radio waves; gamma rays; or x-rays), or a stream of subatomic particles (such as electrons; neutrons; protons; or alpha particles). Osteosarcoma exposure 
  • Can use voiding cystourethrography to diagnose vesicoureteral reflux Vesicoureteral Reflux Vesicoureteral reflux (VUR) is the retrograde flow of urine from the bladder into the upper urinary tract. Primary VUR often results from the incomplete closure of the ureterovesical junction, whereas secondary VUR is due to an anatomic or physiologic obstruction. Vesicoureteral Reflux or bladder Bladder A musculomembranous sac along the urinary tract. Urine flows from the kidneys into the bladder via the ureters, and is held there until urination. Pyelonephritis and Perinephric Abscess neck Neck The part of a human or animal body connecting the head to the rest of the body. Peritonsillar Abscess and urethral obstructions

Management

Treatment

Mainstay of treatment is to relieve the cause of obstruction.

• Urinary tract Urinary tract The urinary tract is located in the abdomen and pelvis and consists of the kidneys, ureters, urinary bladder, and urethra. The structures permit the excretion of urine from the body. Urine flows from the kidneys through the ureters to the urinary bladder and out through the urethra. Urinary Tract: Anatomy obstruction complicated by infection requires immediate relief of the obstruction to prevent sepsis Sepsis Systemic inflammatory response syndrome with a proven or suspected infectious etiology. When sepsis is associated with organ dysfunction distant from the site of infection, it is called severe sepsis. When sepsis is accompanied by hypotension despite adequate fluid infusion, it is called septic shock. Sepsis and Septic Shock and renal damage.
• Drainage may be achieved by nephrostomy tube, ureterostomy, ureteral stent placement, or bladder Bladder A musculomembranous sac along the urinary tract. Urine flows from the kidneys into the bladder via the ureters, and is held there until urination. Pyelonephritis and Perinephric Abscess catheterization.
• Decompression of the urinary system is combined with antibiosis for sepsis-related obstruction. 
• Benign Benign Fibroadenoma prostatic hyperplasia Hyperplasia An increase in the number of cells in a tissue or organ without tumor formation. It differs from hypertrophy, which is an increase in bulk without an increase in the number of cells. Cellular Adaptation can be treated with α-adrenergic blockers or 5α-reductase inhibitors. When associated with severe infection and bladder outlet obstruction Bladder Outlet Obstruction Benign Prostatic Hyperplasia, urethral catheterization is indicated.

Prognosis Prognosis A prediction of the probable outcome of a disease based on a individual’s condition and the usual course of the disease as seen in similar situations. Non-Hodgkin Lymphomas

After relief of obstruction:

• Renal prognosis Prognosis A prediction of the probable outcome of a disease based on a individual’s condition and the usual course of the disease as seen in similar situations. Non-Hodgkin Lymphomas depends on:
  • Presence of irreversible renal damage
  • Severity and duration of obstruction
• Most functional recovery is seen 7–10 days
• Some patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship with severe renal failure Renal failure Conditions in which the kidneys perform below the normal level in the ability to remove wastes, concentrate urine, and maintain electrolyte balance; blood pressure; and calcium metabolism. Renal insufficiency can be classified by the degree of kidney damage (as measured by the level of proteinuria) and reduction in glomerular filtration rate. Crush Syndrome may require dialysis Dialysis Renal replacement therapy refers to dialysis and/or kidney transplantation. Dialysis is a procedure by which toxins and excess water are removed from the circulation. Hemodialysis and peritoneal dialysis (PD) are the two types of dialysis, and their primary difference is the location of the filtration process (external to the body in hemodialysis versus inside the body for PD). Peritoneal Dialysis and Hemodialysis.

With unrelieved obstruction:

• Clinical course depends on whether the obstruction is complete, partial, or bilateral. 
• Complete obstruction that is complicated by infection can lead to complete renal destruction within days.
• Partial recovery of renal function can be seen after 1–2 weeks of complete obstruction.
• After 8 weeks of complete obstruction, recovery is unlikely.