Symptoms (and signs) consistent with renal papillary necrosis are:

Autosomal dominant polycystic kidney disease (ADPKD) is the most prevalent, potentially lethal, monogenic human disorder. It is associated with large interfamilial and intrafamilial variability, which can be explained to a large extent by its genetic heterogeneity and modifier genes. It is also the most common of the inherited cystic kidney diseases — a group of disorders with related but distinct pathogenesis, characterized by the development of renal cysts and various extrarenal manifestations, which in case of ADPKD include cysts in other organs, such as the liver, seminal vesicles, pancreas, and arachnoid membrane, as well as other abnormalities, such as intracranial aneurysms and dolichoectasias, aortic root dilatation and aneurysms, mitral valve prolapse, and abdominal wall hernias. Over 50% of patients with ADPKD eventually develop end stage kidney disease and require dialysis or kidney transplantation. ADPKD is estimated to affect at least 1 in every 1000 individuals worldwide, making this disease the most common inherited kidney disorder with a diagnosed prevalence of 1:2000 and incidence of 1:3000-1:8000 in a global scale.

Acute tubular necrosis is classified as a "renal" (i.e. not pre-renal or post-renal) cause of acute kidney injury. Diagnosis is made by a FENa (fractional excretion of sodium) > 3% and presence of muddy casts (a type of granular cast) in urinalysis. On histopathology, there is usually "tubulorrhexis", that is, localized necrosis of the epithelial lining in renal tubules, with focal rupture or loss of basement membrane. Proximal tubule cells can shed with variable viability and not be purely "necrotic".

Though this condition is usually asymptomatic, if symptoms are present they are usually related to the causative process, (e.g. hypercalcemia). Some of the sympotoms that can happen are blood in the urine, fever and chills, nausea and vomiting, severe pain in the belly area, flanks of the back, groin, or testicles.

These include renal colic, polyuria and polydipsia:

- Renal colic is usually caused by pre-existing nephrolithiasis, as may occur in patients with chronic hypercalciuria. Less commonly, it can result from calcified bodies moving into the calyceal system.

- Nocturia, polyuria, and polydipsia from reduced urinary concentrating capacity (i.e. nephrogenic diabetes insipidus) as can be seen in hypercalcemia, medullary nephrocalcinosis of any cause, or in children with Bartter syndrome in whom essential tubular salt reabsorption is compromised.

There are several causes of nephrocalcinosis that are typically acute and present only with renal failure. These include tumor lysis syndrome, acute phosphate nephropathy, and occasional cases of enteric hyperoxaluria.

Acute tubular necrosis (ATN) is a medical condition involving the death of tubular epithelial cells that form the renal tubules of the kidneys. ATN presents with acute kidney injury (AKI) and is one of the most common causes of AKI. Common causes of ATN include low blood pressure and use of nephrotoxic drugs. The presence of "muddy brown casts" of epithelial cells found in the urine during urinalysis is pathognomonic for ATN. Management relies on aggressive treatment of the factors that precipitated ATN (e.g. hydration and cessation of the offending drug). Because the tubular cells continually replace themselves, the overall prognosis for ATN is quite good if the cause is corrected, and recovery is likely within 7 to 21 days.

While most cases of horseshoe kidneys are asymptomatic and discovered upon autopsy, the condition may increase the risk for:

- Kidney obstruction – abnormal placement of ureter may lead to obstruction and dilation of the kidney.

- Kidney infections – associated with vesicoureteral reflux.

- Kidney stones – deviant orientation of kidneys combined with slow urine flow and kidney obstruction may lead to kidney stones.

- Kidney cancer – increased risk of renal cancer, especially Wilms' tumor, transitional cell carcinoma, and an occasional case report of carcinoid tumor. Despite increased risk, the overall risk is still relatively low.

The prevalence of horseshoe kidneys in females with Turner Syndrome is about 15%.

It can be associated with trisomy 18.

It can be associated with venous anomalies like left sided IVC 9.

In terms of cause, almost any condition that involves ischemia can lead to renal papillary necrosis. A mnemonic for the causes of renal papillary necrosis is POSTCARDS: pyelonephritis, obstruction of the urogenital tract, sickle cell disease, tuberculosis, cirrhosis of the liver, analgesia/alcohol abuse, renal vein thrombosis, diabetes mellitus, and systemic vasculitis. Often, a patient with renal papillary necrosis will have numerous conditions acting synergistically to bring about the disease.

Analgesic nephropathy is a common cause of renal papillary necrosis. The damage is cumulative and most patients of renal papillary necrosis would have ingested at least 2 kg of analgesics in the past. The risk is higher for phenacetin (which was withdrawn from market in the United States) and paracetamol (acetaminophen) compared to aspirin and other NSAIDs.

Nephrocalcinosis Is connected with conditions that cause hypercalcemia, hyperphosphatemia, and the increased excretion of calcium, phosphate, and/or oxalate in the urine. A high urine pH can lead to Nephrocalcinosis. In conjustion with Nephrocalcinosis, hypercalcemia and hypercalciuria the following can occur:

- Primary hyperparathyroidism: Nephrocalcinosis is one of the most common symptoms of primary hyperparathyroidism.

- Sarcoidosis: Nephrocalcinosis is one of the most common symptoms.

- Vitamin D therapy: This can cause nephrocalcinosis because of Vitamin D therapy becauseit increase the absorption of ingested calcium and bone resorption, resulting in hypercalcemia and hypercalciuria.

In patients with this condition, the central portion of the kidney may be found just inferior to the inferior mesenteric artery because the normal embryologic ascent of the kidneys is arrested by its presence in people with central fusion of the kidneys. Horseshoe kidney is often asymptomatic, though persons affected by this condition may experience nausea, abdominal discomfort, kidney stones and urinary tract infections at greater frequency than those without renal fusion. There is currently no treatment for renal fusion other than symptomatic treatment.

Imaging Findings -

The 2 kidneys on opposite sides of the body with the lower poles fused in midline. Midline or symmetrical fusion (90% of cases).

May be missed on US, therefore pay careful attention to identification of lower poles of kidneys.

Renal long axis medially orientated,

Lower poles with curved configuration, elongation and poorly defined

Isthmus crosses midline anterior to spine and great vessels.

US for diagnosis in utero

IVP followed by CT or scintigraphy for pre-operative assessment

Variant arterial supply -

Bilateral renal arteries,

Inferior mesenteric Artery,

Arteries arising from aorta or common iliac, internal iliac, external iliac or inferior mesenteric arteries.

The lower poles of these kidneys fuse in the midline anterior to the aorta and spine. The isthmus is usually located at L4/5 level between the aorta and IMA.

Nuclear medicine (DMSA) scan confirms horseshoe kidney with fusion of both renal lower poles.

Usually, the diagnosis of ADPKD is initially performed by renal imaging using ultrasound, CT scan, or MRI. However, molecular diagnostics can be necessary in the following situations: 1- when a definite diagnosis is required in young individuals, such as a potential living related donor in an affected family with equivocal imaging data; 2- in patients with a negative family history of ADPKD, because of potential phenotypic overlap with several other kidney cystic diseases; 3- in families affected by early-onset polycystic kidney disease, since in this cases hypomorphic alleles and/or oligogenic inheritance can be involved; and 4- in patients requesting genetic counseling, especially in couples wishing a pre-implantation genetic diagnosis.

The findings of large echogenic kidneys without distinct macroscopic cysts in an infant/child at 50% risk for ADPKD are diagnostic. In the absence of a family history of ADPKD, the presence of bilateral renal enlargement and cysts, with or without the presence of hepatic cysts, and the absence of other manifestations suggestive of a different renal cystic disease provide presumptive, but not definite, evidence for the diagnosis. In some cases, intracranial aneurysms can be an associated sign of ADPKD, and screening can be recommended for patients with a family history of intracranial aneurysm.

Molecular genetic testing by linkage analysis or direct mutation screening is clinically available; however, genetic heterogeneity is a significant complication to molecular genetic testing. Sometimes a relatively large number of affected family members need to be tested in order to establish which one of the two possible genes is responsible within each family. The large size and complexity of PKD1 and PKD2 genes, as well as marked allelic heterogeneity, present obstacles to molecular testing by direct DNA analysis. The sensitivity of testing is nearly 100% for all patients with ADPKD who are age 30 years or older and for younger patients with PKD1 mutations; these criteria are only 67% sensitive for patients with PKD2 mutations who are younger than age 30 years.

Renal cysts and diabetes syndrome (RCAD), also known as MODY 5, is a form of maturity onset diabetes of the young.

HNF1β-related MODY is one of the less common forms of MODY, with some distinctive clinical features, including atrophy of the pancreas and several forms of renal disease. HNF1β, also known as transcription factor 2 (TCF2), is involved in early stages of embryonic development of several organs, including the pancreas, where it contributes to differentiation of pancreatic endocrine Ngn3 cell progenitors from non-endocrine embryonic duct cells. The gene is on chromosome 17q.

The degree of insulin deficiency is variable. Diabetes can develop from infancy through middle adult life, and some family members who carry the gene remain free of diabetes into later adult life. Most of those who develop diabetes show atrophy of the entire pancreas, with mild or subclincal deficiency of exocrine as well as endocrine function.

The non-pancreatic manifestations are even more variable. Kidney and genitourinary malformation and diseases may occur, but inconsistently even within a family, and the specific conditions include a range of apparently unrelated anomalies and processes. The most common genitourinary condition is cystic kidney disease, but there are many varieties even of this. Renal effects begin with structural alterations (small kidneys, renal cysts, anomalies of the renal pelvis and calices), but a significant number develop slowly progressive renal failure associated with chronic cystic disease of the kidneys. In some cases, renal cysts may be detected in utero. Kidney disease may develop before or after hyperglycemia, and a significant number of people with MODY5 are discovered in renal clinics.

With or without kidney disease, some people with forms of HNF1β have had various minor or major anomalies of the reproductive system. Male defects have included epididymal cysts, agenesis of the vas deferens, or infertility due to abnormal spermatozoa. Affected women have been found to have vaginal agenesis, hypoplastic, or bicornuate uterus.

Liver enzyme elevations are common, but clinically significant liver disease is not. Hyperuricaemia and early onset gout have occurred.

A renal cyst or kidney cyst, is a fluid collection in or on the kidney. There are several types based on the "Bosniak classification". The majority are benign, simple cysts that can be monitored and not intervened upon. However, some are cancerous or are suspicious for cancer and are commonly removed in a surgical procedure called nephrectomy.

Numerous renal cysts are seen in the cystic kidney diseases, which include polycystic kidney disease and medullary sponge kidney.

Up to 27 percent of individuals greater than 50 years of age may have simple renal cysts that cause no symptoms.

Acute uric acid nephropathy is caused by deposition of uric acid crystals within the kidney interstitium and tubules, leading to partial or complete obstruction of collecting ducts, renal pelvis, or ureter. This obstruction is usually bilateral, and patients follow the clinical course of acute renal failure.

The hallmark of a stone that obstructs the ureter or renal pelvis is excruciating, intermittent pain that radiates from the flank to the groin or to the inner thigh. This pain, known as renal colic, is often described as one of the strongest pain sensations known. Renal colic caused by kidney stones is commonly accompanied by urinary urgency, restlessness, hematuria, sweating, nausea, and vomiting. It typically comes in waves lasting 20 to 60 minutes caused by peristaltic contractions of the ureter as it attempts to expel the stone.

The embryological link between the urinary tract, the genital system, and the gastrointestinal tract is the basis of the radiation of pain to the gonads, as well as the nausea and vomiting that are also common in urolithiasis. Postrenal azotemia and hydronephrosis can be observed following the obstruction of urine flow through one or both ureters.

Pain in the lower left quadrant can sometimes be confused with diverticulitis because the sigmoid colon overlaps the ureter and the exact location of the pain may be difficult to isolate due to the close proximity of these two structures.

The prognosis for nephrotic syndrome under treatment is generally good although this depends on the underlying cause, the age of the patient and their response to treatment. It is usually good in children, because minimal change disease responds very well to steroids and does not cause chronic renal failure. Any relapses that occur become less frequent over time; the opposite occurs with mesangiocapillary glomerulonephritis, in which the kidney fails within three years of the disease developing, making dialysis necessary and subsequent kidney transplant. In addition children under the age of 5 generally have a poorer prognosis than prepubescents, as do adults older than 30 years of age as they have a greater risk of kidney failure.

Other causes such as focal segmental glomerulosclerosis frequently lead to end stage renal disease. Factors associated with a poorer prognosis in these cases include level of proteinuria, blood pressure control and kidney function (GFR).

Without treatment nephrotic syndrome has a very bad prognosis especially "rapidly progressing glomerulonephritis", which leads to acute kidney failure after a few months.

The buildup of oxalate in the body causes increased renal excretion of oxalate (hyperoxaluria), which in turn results in renal and bladder stones. Stones cause urinary obstruction (often with severe and acute pain), secondary infection of urine and eventually kidney damage.

Oxalate stones in primary hyperoxaluria tend to be severe, resulting in relatively early kidney damage (say teenage, early adulthood), which impairs the excretion of oxalate leading to a further acceleration in accumulation of oxalate in the body.

After the development of renal failure patients may get deposits of oxalate in the bones, joints and bone marrow. Severe cases may develop haematological problems such as anaemia and thrombocytopaenia. The deposition of oxalate in the body is sometimes called "oxalosis" to be distinguished from "oxaluria" which refers to oxalate in the urine.

Renal failure is a serious complication requiring treatment in its own right. Dialysis can control renal failure but tends to be inadequate to dispose of excess oxalate. Renal transplant is more effective and this is the primary treatment of severe hyperoxaluria. Liver transplantation (often in addition to renal transplant) may be able to control the disease by correcting the metabolic defect.

In a proportion of patients with primary hyperoxaluria type 1 (about 5%), pyridoxine treatment (vitamin B6) may decrease oxalate excretion and prevent kidney stone formation.

Primary hyperoxaluria is an autosomal recessive disease, meaning both copies of the gene contain the mutation. Both parents must have one copy of this mutated gene to pass it on to their child, but they do not typically show signs or symptoms of the disease.

Acute uric acid nephropathy (AUAN, also acute urate nephropathy) is a rapidly worsening (decreasing) kidney function (renal insufficiency) that is caused by high levels of uric acid in the urine (hyperuricosuria).

Nephrotic syndrome is a collection of symptoms due to kidney damage. This includes protein in the urine, low blood albumin levels, high blood lipids, and significant swelling. Other symptoms may include weight gain, feeling tired, and foamy urine. Complications may include blood clots, infections, and high blood pressure.

Causes include a number of kidney diseases such as focal segmental glomerulosclerosis, membranous nephropathy, and minimal change disease. It may also occur as a complication of diabetes or lupus. The underlying mechanism typically involves damage to the glomeruli of the kidney. Diagnosis is typically based on urine testing and sometimes a kidney biopsy. It differs from nephritic syndrome in that there are no red blood cells in the urine.

Treatment is directed at the underlying cause. Other efforts include managing high blood pressure, high blood cholesterol, and infection risk. A low salt diet and limiting fluids is often recommended. About 5 per 100,000 people are affected per year. The usual underlying cause varies between children and adults.

Primary hyperoxaluria is a rare condition (autosomal recessive), resulting in increased excretion of oxalate (up to 600mg a day from normal 50mg a day), with oxalate stones being common.

Urolithiasis refers to stones originating anywhere in the urinary system, including the kidneys and bladder. Nephrolithiasis refers to the presence of such stones in the kidneys. Calyceal calculi are aggregations in either the minor or major calyx, parts of the kidney that pass urine into the ureter (the tube connecting the kidneys to the urinary bladder). The condition is called ureterolithiasis when a calculus is located in the ureter. Stones may also form or pass into the bladder, a condition referred to as bladder stones.

Conorenal syndrome, also called Mainzer-Saldino syndrome or Saldino-Mainzer disease, is a collection of medical conditions that seem to have a common genetic cause.

Inborn errors of renal tubular transport are metabolic disorders which lead to impairment in the ability of solutes, such as salts or amino acids, to be transported across the brush border of the renal tubule. This results in disruptions of renal reabsorption.

Examples of these disorders include Iminoglycinuria, renal tubular acidosis and Gitelman syndrome.

Renal failure is defined by functional impairment of the kidney. Renal failure can be acute or chronic, and can be further broken down into categories of pre-renal, intrinsic renal and post-renal.

Pre-renal failure refers to impairment of supply of blood to the functional nephrons including renal artery stenosis. Intrinsic renal diseases are the classic diseases of the kidney including drug toxicity and nephritis. Post-renal failure is outlet obstruction after the kidney, such as a kidney stone or prostatic bladder outlet obstruction.

Renal failure may require medication, dietary and lifestyle modification and dialysis.

Primary renal cell carcinomas as well as metastatic cancers can affect the kidney.

Kidney tumours may be discovered on medical imaging incidentally (i.e. an incidentaloma), or may be present in patients as an abdominal mass or kidney cyst, hematuria, abdominal pain, or manifest first in a paraneoplastic syndrome that seems unrelated to the kidney.