Hydronephrosis
Encyclopedia
Hydronephrosis is distension and dilation
of the renal pelvis
calyces
, usually caused by obstruction
of the free flow of urine from the kidney
, leading to progressive atrophy
of the kidney. In cases of hydroureteronephrosis, there is distention of both the ureter and the renal pelvis and calices.
Blood tests can show raised creatinine, urea and electrolyte imbalance. A urine test may show an elevated pH due to the secondary destruction of nephrons within the affected kidney. An enlarged kidney may be palpable upon examination.
Compression of one or both ureters can also be caused by other developmental defects not completely occurring during the fetal stage such as an abnormally placed vein, artery, or tumor. Bilateral compression of the ureters can occur during pregnancy due to enlargement of the uterus. Changes in hormone levels during this time may also affect the muscle contractions of the bladder, further complicating this condition.
Sources of obstruction that can arise from other various causes include kidney stones and blood clots.
The obstruction may be either partial or complete and can occur anywhere from the urethral meatus
to the calyces
of the renal pelvis
.
Hydronephrosis can also result from the reverse flow of urine from the bladder back into the kidneys. This reflux can be caused by some of the factors listed above as well as compression of the bladder outlet into the urethra by prostatic enlargement or impaction of feces in the colon, as well as abnormal contractions of bladder muscles resulting from neurological dysfunction or other muscular disorders.
Prenatal diagnosis is possible.
Blood (U&E, creatinine) and urine (MSU, pH) tests should be taken. An Intravenous Urogram (IVU), ultrasound, CT or MRI are also important investigations in determining the presence and/ or cause of hydronephrosis. Whilst ultrasound allows for visualisation of the ureters and kidneys (and determine the presence of hydronephrosis and / or hydroureter), an IVU is useful for assessing the anatomical location of the obstruction. Antegrade or retrograde pyelography will show similar findings to an IVU but offer a therapeutic option as well.
The choice of imaging depends on the clinical presentation (history, symptoms and examination findings). In the case of renal colic
(one sided loin pain usually accompanied by a trace of blood in the urine) the initial investigation is usually a spiral or helical CT scan. This has the advantage of showing whether there is any obstruction of flow of urine causing hydronephrosis as well as demonstrating the function of the other kidney. Many stones are not visible on plain X-ray
or IVU but 99% of stones are visible on CT and therefore CT is becoming a common choice of initial investigation. CT is not used however, when there is a reason to avoid radiation exposure, e.g. in pregnancy.
s rather than one) has a poor prognosis
.
.
Acute obstruction of the upper urinary tract is usually treated by the insertion of a nephrostomy
tube. Chronic upper urinary tract obstruction is treated by the insertion of a ureteric stent
or a pyeloplasty
.
Lower urinary tract obstruction (such as that caused by bladder outflow obstruction secondary to prostatic hypertrophy) is usually treated by insertion of a urinary catheter or a suprapubic catheter.
Surgery is not required in all cases.
Dilation
Dilation refers to an enlargement or expansion in bulk or extent, the opposite of contraction. It derives from the Latin dilatare, "to spread wide".In physiology:* Pupillary dilation, dilation of the pupil of the eye...
of the renal pelvis
Renal pelvis
The renal pelvis or pyelum is the funnel-like dilated proximal part of the ureter in the kidney.In humans, the renal pelvis is the point of convergence of two or three major calyces...
calyces
Calyx (kidney)
Calyx may refer to:* Major calyx* Minor calyx...
, usually caused by obstruction
Obstruction
Obstruction may refer to:* Obstruction theory, in mathematics* Obstruction of justice, the crime of interfering with law enforcement* Obstructing government administration* Propagation path obstruction** Single Vegetative Obstruction Model-Medical:...
of the free flow of urine from the kidney
Kidney
The kidneys, organs with several functions, serve essential regulatory roles in most animals, including vertebrates and some invertebrates. They are essential in the urinary system and also serve homeostatic functions such as the regulation of electrolytes, maintenance of acid–base balance, and...
, leading to progressive atrophy
Atrophy
Atrophy is the partial or complete wasting away of a part of the body. Causes of atrophy include mutations , poor nourishment, poor circulation, loss of hormonal support, loss of nerve supply to the target organ, disuse or lack of exercise or disease intrinsic to the tissue itself...
of the kidney. In cases of hydroureteronephrosis, there is distention of both the ureter and the renal pelvis and calices.
Signs and symptoms
The signs and symptoms of hydronephrosis depend upon whether the obstruction is acute or chronic, partial or complete, unilateral or bilateral. Hydronephrosis that occurs acutely with sudden onset (as caused by a kidney stone) can cause intense pain in the flank area (between the hips and ribs), while a chronic occurrence that develops gradually will present with no pain or attacks of a dull discomfort. Nausea and vomiting may also occur. An obstruction that occurs at the urethra or bladder outlet can cause pain and pressure resulting from distension of the bladder. Blocking the flow of urine will commonly result in urinary tract infections which can lead to the development of additional stones, fever, and blood or pus in the urine. If complete obstruction occurs, kidney failure may follow.Blood tests can show raised creatinine, urea and electrolyte imbalance. A urine test may show an elevated pH due to the secondary destruction of nephrons within the affected kidney. An enlarged kidney may be palpable upon examination.
Causes
Hydronephrosis is the result of several abnormal pathophysiological occurrences. Structural abnormalities of the junctions between the kidney, ureter, and bladder that lead to hydronephrosis can occur during fetal development. Some of these congenital defects have been identified as inherited conditions, however the benefits of linking genetic testing to early diagnosis have not been determined. Other structural abnormalities could be caused by injury, surgery, or radiation therapy.Compression of one or both ureters can also be caused by other developmental defects not completely occurring during the fetal stage such as an abnormally placed vein, artery, or tumor. Bilateral compression of the ureters can occur during pregnancy due to enlargement of the uterus. Changes in hormone levels during this time may also affect the muscle contractions of the bladder, further complicating this condition.
Sources of obstruction that can arise from other various causes include kidney stones and blood clots.
The obstruction may be either partial or complete and can occur anywhere from the urethral meatus
Urinary meatus
The urinary meatus is an orifice of the urethra. It is the point at which urine and, in males, semen exits the urethra. The meatus features varying degrees of sensitivity to the touch among males and females....
to the calyces
Minor calyx
The minor calyx, in the kidney, surrounds the apex of the renal pyramids. Urine formed in the kidney passes through a papilla at the apex into the minor calyx then into the major calyx....
of the renal pelvis
Renal pelvis
The renal pelvis or pyelum is the funnel-like dilated proximal part of the ureter in the kidney.In humans, the renal pelvis is the point of convergence of two or three major calyces...
.
Hydronephrosis can also result from the reverse flow of urine from the bladder back into the kidneys. This reflux can be caused by some of the factors listed above as well as compression of the bladder outlet into the urethra by prostatic enlargement or impaction of feces in the colon, as well as abnormal contractions of bladder muscles resulting from neurological dysfunction or other muscular disorders.
Pathophysiology
Obstruction that occurs anywhere along the upper urinary tract will lead to increased pressure within the structures of the kidney due to the inability to pass urine from the kidney to the bladder. Obstruction occurring in the lower urinary tract can cause this increased pressure through the reflux of urine into the kidney. All of these factors will lead to the destruction of the delicate tissues that make up the filtration system within the kidneys, which could eventually result in infection, stone formation, or loss of function. Additional complications arising from obstruction of the lower urinary tract include the stagnation of urine flow which can also lead to infection in the bladder.Diagnosis
Blood (U&E, creatinine) and urine (MSU, pH) tests should be taken. An Intravenous Urogram (IVU), ultrasound, CT or MRI are also important investigations in determining the presence and/ or cause of hydronephrosis. Whilst ultrasound allows for visualisation of the ureters and kidneys (and determine the presence of hydronephrosis and / or hydroureter), an IVU is useful for assessing the anatomical location of the obstruction. Antegrade or retrograde pyelography will show similar findings to an IVU but offer a therapeutic option as well.
The choice of imaging depends on the clinical presentation (history, symptoms and examination findings). In the case of renal colic
Renal colic
Renal colic is a type of abdominal pain commonly caused by kidney stones.-Presentation:The pain typically begins in the abdomen and often radiates to the hypochondrium or the groin. The pain is often colicky due to ureteric peristalsis, but may be constant...
(one sided loin pain usually accompanied by a trace of blood in the urine) the initial investigation is usually a spiral or helical CT scan. This has the advantage of showing whether there is any obstruction of flow of urine causing hydronephrosis as well as demonstrating the function of the other kidney. Many stones are not visible on plain X-ray
X-ray
X-radiation is a form of electromagnetic radiation. X-rays have a wavelength in the range of 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz and energies in the range 120 eV to 120 keV. They are shorter in wavelength than UV rays and longer than gamma...
or IVU but 99% of stones are visible on CT and therefore CT is becoming a common choice of initial investigation. CT is not used however, when there is a reason to avoid radiation exposure, e.g. in pregnancy.
Prognosis
Left untreated, bilateral obstruction (occurring to both kidneyKidney
The kidneys, organs with several functions, serve essential regulatory roles in most animals, including vertebrates and some invertebrates. They are essential in the urinary system and also serve homeostatic functions such as the regulation of electrolytes, maintenance of acid–base balance, and...
s rather than one) has a poor prognosis
Prognosis
Prognosis is a medical term to describe the likely outcome of an illness.When applied to large statistical populations, prognostic estimates can be very accurate: for example the statement "45% of patients with severe septic shock will die within 28 days" can be made with some confidence, because...
.
Treatment
Treatment of hydronephrosis focuses upon the removal of the obstruction and drainage of the urine that has accumulated behind the obstruction. Therefore, the specific treatment depends upon where the obstruction lies, and whether it is acute or chronicChronic (medicine)
A chronic disease is a disease or other human health condition that is persistent or long-lasting in nature. The term chronic is usually applied when the course of the disease lasts for more than three months. Common chronic diseases include asthma, cancer, diabetes and HIV/AIDS.In medicine, the...
.
Acute obstruction of the upper urinary tract is usually treated by the insertion of a nephrostomy
Nephrostomy
A nephrostomy is an artificial opening created between the kidney and the skin which allows for the urinary diversion directly from the upper part of the urinary system ....
tube. Chronic upper urinary tract obstruction is treated by the insertion of a ureteric stent
Ureteric stent
A ureteral stent, sometimes as well called ureteric stent, is a thin tube inserted into the ureter to prevent or treat obstruction of the urine flow from the kidney. The length of the stents used in adult patients varies between 24 to 30 cm. Additionally, stents come in differing diameters or...
or a pyeloplasty
Pyeloplasty
Pyeloplasty is the surgical reconstruction or revision of the renal pelvis to drain and decompress the kidney. Most commonly it is performed to treat an uretero-pelvic junction obstruction if residual renal function is adequate....
.
Lower urinary tract obstruction (such as that caused by bladder outflow obstruction secondary to prostatic hypertrophy) is usually treated by insertion of a urinary catheter or a suprapubic catheter.
Surgery is not required in all cases.