Overview
Due to congenital or acquired causes of the absence of one side of the kidney, the opposite side of the kidney is called isolated kidney early stage may not have obvious clinical manifestations, some patients may appear proteinuria, hypertension and other symptoms can be formed by congenital or due to living donor kidney, as well as urological tumors, trauma, tuberculosis, stones, etc. lead to unilateral nephrectomy is mainly taken by the general treatment, medication, renal replacement therapy, surgical treatment and so on.
Definition
Isolated kidney (SK) is relatively common in clinical practice, mainly including congenital isolated kidney and acquired isolated kidney. It may be congenital isolated kidney due to the lack of development or poor development of one side of the kidney, or acquired isolated kidney due to the removal of one side of the kidney by renal tumor, trauma, tuberculosis, living donor kidney and other reasons [1].
Classification
Congenital isolated kidney and acquired isolated kidney can be categorized according to the etiology.
Congenital isolated kidney
It is characterized by unilateral renal agenesis, atrophy or non-function at birth [2].
Acquired isolated kidney
It is caused by the removal of one side of the kidney due to various reasons, mainly including urological diseases (such as tumors, tuberculosis, stones, etc.), trauma, and living kidney donation.
Incidence
The incidence of congenital isolated kidney is about 0.05%, i.e., about 1 in 2000 people [3]. The incidence of acquired isolated kidney is unknown due to lack of large epidemiologic studies.
The prevalence of left renal agenesis is higher, with a higher prevalence in males than females in the same age group [4]. There is a population of approximately 1.3 million isolated kidneys in China [5].
Causes
Pathogenesis
Isolated kidneys are formed congenitally or due to living donor kidneys, and can also be caused by other causes such as urological tumors, trauma, tuberculosis, and stones that lead to the resection of one side of the kidney [6].
Congenital formation
Congenital isolated kidney is one of the common phenotypes of congenital malformations of renal and urinary tract development and a major cause of end-stage renal disease in children, which refers to the failure of unilateral embryonic kidney formation due to embryonic underdevelopment, which leads to congenital absence of renal tissue [7].
Living donor kidney
Currently, the number of living donor kidney transplants has been steadily increasing, making living donor kidneys the leading cause of acquired isolated kidneys [8].
Urologic diseases
They mainly include renal tumors, renal tuberculosis, renal stones, and renal trauma.
Currently, the clinically recognized gold standard for the treatment of renal cancer is radical nephrectomy, which removes the affected kidney, which can lead to the formation of an isolated kidney [9].
When patients with renal tuberculosis have severe renal lesions on one side of the kidney without significant impairment of renal function on the opposite side, the affected kidney may be removed, leading to the formation of an isolated kidney [10].
If stones cause severe destruction of renal structure and loss of function, or are combined with renal pus, and the contralateral kidney is functioning well, the affected kidney may be resected, leading to isolated kidney formation [11].
When severe total renal laceration or trauma to the renal hilum vasculature is irreparable and the contralateral kidney is functioning well, nephrectomy of the injured side is feasible, leading to isolated kidney formation [11].
High-risk factors
The following factors are high-risk factors for isolated kidney and may cause the development or exacerbation of the disease.
Adverse lifestyle habits, such as high salt and high protein diet, smoking and drinking, staying up late and being overweight.
Long-term application of nephrotoxic drugs, including aminoglycoside antibiotics (e.g. gentamicin, streptomycin), non-steroidal anti-inflammatory drugs (e.g. ibuprofen, acetaminophen), interferon, methimazole, and traditional Chinese medicines (e.g. guanmutong, guanpengi) containing aristolochic acid.
Not taking proper protective measures when performing activities that may cause kidney trauma such as sledding, skiing, rollerblading, horseback riding, etc. [3].
Patients with a history of tuberculosis and urinary stones are not treated in a standardized manner in the early stages of the disease.
Previous history of urological tumors, not treated in time or poorly treated.
Symptoms
Due to the strong compensatory ability of the kidney, isolated kidney usually has no obvious clinical manifestations in the early stage, and is often found incidentally when imaging tests are done for other diseases [1]. Some patients may have symptoms such as proteinuria and hypertension.
Main symptoms
proteinuria
Isolated renal compensatory hypertrophy and hyperfiltration may lead to persistent proteinuria. The main clinical manifestation is the presence of foam in the urine, which does not disappear for a prolonged period of time. In addition, there is evidence that patients with surgical removal of one kidney are at a higher risk of hypertension and proteinuria compared to patients with congenitally isolated kidneys [12].
Hypertension.
Isolated kidneys may also lead to decreased intrarenal perfusion pressure, causing increased angiotensin II activity and systemic constriction of the walls of small arterial vessels resulting in hypertension, which may be manifested as dizziness, headache, and vomiting.
Complications
Chronic renal failure
With the progressive aggravation of renal damage, some patients may develop chronic renal failure.
It mainly manifests symptoms such as weakness, nausea, poor appetite, lumbago, etc. In severe cases, shortness of breath, dyspnea, delirium, coma, etc. may also occur [13].
Consultation
Department of Medicine
Nephrology
When symptoms such as foam in the urine do not go away for a long period of time, it is recommended to consult a nephrologist promptly.
Emergency department
If you experience symptoms such as severe headache, difficulty breathing, delirium, or coma, it is recommended that you consult the Emergency Department promptly.
Preparation for medical treatment
Preparation for medical consultation: registration, preparation of documents, common problems
Tips for medical treatment
It is recommended to wear loose-fitting clothes to the clinic, so as to facilitate the whole body physical examination.
Record the changes and characteristics of your condition to give your doctor more reference.
Preparation Checklist
Symptom list
Pay particular attention to the time of onset of symptoms, special manifestations, etc.
Is there foam in the urine? How long does the foam in the urine last?
Has there been a recent unexplained increase in blood pressure?
Medical history
Is there any history of congenital loss of kidney tissue?
Has there been any previous living kidney donation?
Any nephrectomy due to urinary tumor, trauma, tuberculosis, stones, etc.?
Checklist
Test results in the last six months, which can be brought to the doctor’s office
Laboratory tests: blood routine, urine test, blood biochemistry (liver function, kidney function, electrolytes), serum cystatin C, etc.
Imaging tests: renal ultrasound, CT examination, intravenous urography.
Cystoscopy.
Medication list
Medication use in the last 3 months, if available in boxes or packages, bring with you to the doctor’s office
ACEI (Prilosec)/ARB (Sartans) drugs: captopril, irbesartan, etc.
Antipyretic and analgesic medications: e.g., ibuprofen, acetaminophen, etc.
Diagnosis
Isolated kidney can be diagnosed according to the patient’s imaging, and the etiology of isolated kidney, renal lesions and renal function abnormalities can be clarified according to the history, clinical manifestations, and relevant laboratory tests.
Diagnostic basis
Medical history
The following is not necessary for the diagnosis of the disease, but if there is the following medical history, it can provide some reference significance for the diagnosis of the disease.
History of congenital loss of renal tissue.
Previous living donor kidney.
Previous nephrectomy for urologic tumor, trauma, tuberculosis, stones, etc.
Clinical manifestations
Early stage patients may have no special manifestations, some patients may have proteinuria, hypertension and other symptoms.
Laboratory Tests
Routine blood test
It is mainly to know whether the patient has any abnormalities in the blood system.
When hemoglobin, erythrocyte pressure and count are decreased to different degrees, it suggests that anemia may occur, which is of some significance in the diagnosis of the disease.
Urine examination
It mainly includes urine routine and urine albumin/creatinine ratio.
Urine routine mainly evaluates the presence of hematuria, proteinuria, etc. If abnormal, it suggests the possible existence of renal lesions.
The urine albumin/creatinine ratio is easy to obtain and helps to evaluate the degree of albuminuria.
Blood biochemistry
It mainly includes liver function, renal function and electrolytes.
Alanine aminotransferase and aspartate aminotransferase in liver function tests can understand the level of liver function, which has a certain significance in guiding the use of drugs [14].
When the renal function of urea nitrogen and blood creatinine are elevated to different degrees, it usually suggests that the renal function is impaired, which helps to assess the prognosis of the disease and guide the treatment.
When the disease progresses to chronic renal failure, high potassium, low calcium, high phosphorus and other manifestations may occur, electrolyte examination can help timely diagnosis and treatment of the disease.
Serum cystatin C
It is mainly to understand the degree of early damage to renal function.
Serum cystatin C has high specificity and sensitivity in the diagnosis of early renal impairment, and has guiding value in the early diagnosis of renal diseases [14].
Imaging examination
Renal ultrasound
Renal ultrasound can be used to understand and indicate the presence or absence of isolated kidneys as well as renal lesions.
In the early stage of the disease, the size of the kidney is normal or mildly enlarged.
CT examination
A CT scan is used to visualize the patient’s kidneys.
CT examination can clarify whether one side of the kidney is missing, and also helps to know whether there is ectopic kidney, which is important for the diagnosis and differential diagnosis of the disease.
Intravenous urography
Intravenous urography is mainly used to find out whether congenital isolated kidney is accompanied by other systemic malformations or urinary tract related diseases.
Intravenous urography has certain significance in the diagnosis of urinary stones, tumors, tuberculosis and congenital malformations.
Cystoscopy
Cystoscopy is mainly used to find out whether there is a ureter and whether the opening is normal.
If the kidney is congenitally isolated, cystoscopy can see the asymmetry of the triangle and the absence of one side of the ureteral orifice, which is of some significance to the diagnosis of the disease.
Differential diagnosis
Isolated kidney generally needs to be differentiated from cross ectopic kidney, thoracic ectopic kidney and other diseases.
Cross ectopic kidney
Similarity: Both imaging may show absence of one side of the kidney.
Difference: Cross ectopic kidney is a rare congenital genitourinary malformation. In some patients, the ectopic kidney is usually fused underneath the normal kidney, often accompanied by malrotation of the kidney, which is prone to urinary tract obstruction and cause hydronephrosis, infection and stone.
Thoracic ectopic kidney
Similarity: Both of them can be characterized by absence of one side of the kidney in the normal renal region.
Differences: Thoracic ectopic kidneys are extremely rare, due to the abnormal origin of the blood vessels supplying the kidneys during embryonic development, which causes the kidneys to rise up and exceed the normal position to form a high kidney, although it is not seen in the normal renal region on imaging, but both kidneys are intact and there is no agenesis [15].
Treatment
Aims of treatment: to prevent progressive deterioration of renal function and to improve or alleviate clinical symptoms.
Treatment principle: if there are no symptoms usually do not need special treatment; if there are symptoms and complications, the causative factors can be removed and the treatment can be directed to the cause, mainly adopting general treatment, drug treatment and renal replacement therapy. If the congenital isolated kidney is accompanied by malformations of other systems (such as reproductive system, skeletal system, etc.) or associated with urological diseases, surgical treatment is required.
General treatment
Take rest and avoid exertion.
Low-salt, low-fat, high-quality, low-protein diet, with protein intake controlled at less than 1 g per kilogram of body weight per day and daily salt intake less than 4 g [16].
Avoid long-term application of nephrotoxic drugs such as gentamicin, streptomycin, ibuprofen, acetaminophen, methimazole. Avoid taking Guanmutong, Guangpengi, etc.
Medication
ACEI/ARB antihypertensive drugs
Commonly used drugs are ACEI class such as Benadryl, Captopril, ARB class such as Valsartan, Irbesartan, and so on.
It is suitable for patients with elevated blood pressure and proteinuria [17].
The use of the process should pay attention to monitoring blood creatinine and blood potassium levels, severe renal insufficiency caution, allergy, hyperkalemia, pregnant women and renal artery stenosis is prohibited.
Renal replacement therapy
Renal replacement therapy includes hemodialysis, peritoneal dialysis and kidney transplantation.
It is mainly indicated for patients whose disease has progressed to end-stage renal disease. In case of obvious pulmonary edema, hyperkalemia, heart failure and other life-threatening conditions and conservative treatment is ineffective, emergency dialysis treatment is feasible.
Surgery
If congenital isolated kidney is accompanied by malformations of other systems (e.g. reproductive system, cardiovascular system, skeletal system, etc.) or associated urological diseases (e.g. renal stone, hydronephrosis, pyelo-ureteral stenosis, renal mass, etc.), relevant surgical treatments may be required.
Prognosis
Cure
Isolated kidney cannot be cured, but most patients usually do not have any symptoms and the prognosis is generally good.
However, if the kidney is overburdened, resulting in impaired renal function, and if the patient does not receive standardized and effective treatment in a timely manner, the patient may develop chronic renal failure as the disease progresses, in which case the prognosis is not good.
Prognostic factors
The prognosis of isolated kidney is affected by many factors, and the following factors may lead to poor prognosis.
Poor lifestyle, such as high salt and high protein diet, long-term smoking, drinking and staying up late.
Suffering from chronic underlying diseases such as hypertension, diabetes, and poor control of blood glucose and blood pressure levels.
Those who fail to diagnose or treat the disease in a timely manner, as well as those who fail to monitor their condition, leading to disease progression.
Daily
Daily Management
Dietary management
Low-salt diet, avoid pickles and cured meat products, etc.
Low-fat diet, should consume less food rich in saturated fatty acids (animal fats and oils) and more food rich in polyunsaturated fatty acids (e.g. vegetable oils, fish oils) and soluble fiber (e.g. oatmeal, rice bran and beans).
Increase the intake of vitamins as appropriate, such as fresh vegetables and fruits, and moderate consumption of fish, eggs and lean meat.
Life Management
Ensure adequate rest and sleep and avoid overwork.
Participate in physical activities in moderation and control body weight. Some studies have shown that the cardiopulmonary compliance of children with congenital isolated kidney is improved after participating in physical exercise [18].
Appropriately reduce impact sports such as horseback riding and extreme skiing to avoid trauma [5].
Psychological support
It is recommended that the patient’s family members often encourage and comfort the patient, so that the patient reduces psychological pressure, stabilizes mood, avoids anxiety and depression, treats the disease correctly, establishes confidence, and actively cooperates with the treatment.
Disease monitoring
Pay attention to monitoring whether there are bubbles in the urine and the color of urine.
Monitor blood pressure daily.
Follow-up review
Adjust the drug dosage according to the results of the follow-up examination. Regular follow-up can keep abreast of the changes in the condition and provide early symptomatic treatment, which can delay the progression of the disease and prevent the occurrence of complications.
Regular checkups should be conducted according to the doctor’s instructions, and the cycle of checkups usually lasts for 1 to 3 months.
Blood tests, urine tests, blood biochemistry, cystatin C and other related tests may be required for follow-up.
Prevention
The cause of isolated kidney is complex and difficult to prevent effectively, but it can help to reduce the risk of developing the disease through the following healthy lifestyles or behaviors, etc.
Low-salt, low-fat, high-quality and low-protein diet, avoid spicy and stimulating food.
Pay attention to rest, avoid over-exertion, moderate exercise, and control weight.
Avoid long-term use of nephrotoxic drugs, including aminoglycoside antibiotics (e.g., gentamicin, streptomycin), nonsteroidal anti-inflammatory drugs (e.g., ibuprofen, acetaminophen), interferon, methimazole, and traditional Chinese medicines (e.g., guanmutong, guanpengi) containing aristolochic acid.
Take protective measures when performing activities such as sledding, skiing, rollerblading, horseback riding, etc. to avoid trauma.
Regular checkups are recommended for people with urinary tract tumors, tuberculosis, stones, and trauma.