Useful Medical Information




Every organism needs energy and this energy comes from a series of reactions that take place inside cells.
The ingredients necessary to produce energy are contained in the food we consume every day.
Apart from energy production, these chemical reactions also release useful, as well as harmful (toxic) substances, which must be retained or discharged respectively.
The kidney is primarily responsible for this process, so it may be described as the body’s "filter".


The human body has two kidneys that have the shape of a bean. They are located just below the rib cage in the rear part of the peritoneal cavity.
Their main function is to maintain homeostasis with regard to water, electrolytes (such as potassium, sodium, calcium, phosphorus and magnesium), acid-base balance (PH, CO2, HCO3) and many other solutes (such as urea, creatinine, glucose, amino acids, albumins).

Kidneys produce hormones (renin, vitamin D, erythropoietin, prostaglandins) and process hormones (vasopressin, aldosterone, atrial natriuretic peptide, parathyroid hormone).

Kidneys influence and are influenced by almost all systems of the body.
Diseases, such as hypertension, diabetes, rheumatoid arthritis, systemic lupus erythematosus, vasculitis, some hereditary diseases, as well as certain drugs (antibiotics, anti-inflammatories) and normal conditions, such as pregnancy, may affect the structure and function of kidneys.



Renal function disorders are roughly divided into two main categories; reversible and irreversible.

The first category can lead to acute renal failure and the second to chronic renal failure.

A number of people who suffer from chronic kidney disease will be ultimately subjected to extra-renal support, such as periodic hemodialysis or peritoneal dialysis or kidney transplantation.

There are many causes that can lead to acute renal failure. These may either be prerenal (dehydration, reduced blood flow to the kidney), intrinsic (obstruction of the renal artery or vein, glomerulonephritis, endogenous-exogenous toxins, intrarenal obstruction, intrarenal vascular disease), or postrenal (obstruction of the urinary tract, such as tumors, lithiasis).

When the overall renal function is not restored following an episode of acute renal failure within a period of 6 months, then the patient develops chronic renal failure.

Renal disorders lead to various problems, sometimes life-threatening, that result from hyperkalemia, metabolic acidosis and pulmonary edema.

The uremic syndrome refers to the complications of chronic renal failure.

Some of the complications of renal failure are anemia, dehydration, itching, dry skin, skin pigmentation, nausea, vomiting, anorexia, bone disease, libido disorders, impotence, fatigue, confusion, asterixis, seizures, peripheral neuropathy, myopathy, coma, hypertension, pericardial effusion, peripheral edema, sleep disorders, restless legs, muscle cramps, anxiety, depression, and susceptibility to infections. Early diagnosis increases the chance of avoiding serious and life-threatening complications.



Healthy kidneys perform three basic functions:

1.    They remove toxins from the blood through urine production.

2.    They regulate the levels of fluids and electrolytes that are essential to the body.

3.    They have an endocrine function that involves hormone production.

Chronic renal failure is the progressive and irreversible loss of kidney function.

Chronic kidney disease is divided into five stages:

1.    Stage 1: renal failure with normal or increased GFR> 90 ml/min/1.73 m2

2.    Stage 2: slight GFR decrease: 60 - 89 ml/min/1,73 m2

3.    Stage 3: Moderate GFR reduction: 30 - 59 ml/min/1,73 m2

4.    Stage 4: significant GFR reduction: 15 - 29 ml/min/1,73 m2

5.    Stage 5: renal failure - GFR <15 ml/min/1,73 m2

In stage 5, kidneys can no longer function and kidney substitution of renal function is necessary.
Unfortunately, chronic renal failure symptoms are often very mild and thus there is a long delay in diagnosis and treatment thereof.
The causes of chronic renal failure are:

1.    Diabetes mellitus type I and II, which is now the leading cause

2.    Hypertension

3.    Glomerulonephritis (primary and secondary).

4.    Renal lithiasis and kidney infections (pyelonephritis).

5.    Hereditary diseases of the kidneys of which the most common is polycystic kidney disease (PKD).

6.    Chemicals, heavy metals and toxic substances.

Unfortunately, symptoms of early stage chronic renal failure are very mild and thus there is a long delay in diagnosis and treatment thereof.

Depending on the system affected, the following symptoms develop:

  1. Cardiovascular system

o    Pericarditis

o    Arrhythmias

o    Left Ventricular Hypertrophy

o    Heart failure

o    Coronary Disease

  1. Respiratory system

o    Non-cardiogenic pulmonary edema (uremic lung)

o    Pleurisy

  1. Hematopoietic system

o    Anemia

o    Haemorrhagic diathesis

o    Immune disorders

  1. Gastrointestinal system

o    Anorexia, nausea, vomiting, taste disorders

o    Gastritis

o    Peptic ulcer

  1. Central nervous system

o    Irritability, insomnia, lethargy, convulsions, coma

  1. Peripheral nervous system

o     Restless legs syndromeν

  1. Musculoskeletal system

o    Muscle aches, muscle weakness

o    Gouty arthritis - pseudogout

o    Carpal Tunnel Syndrome

  1. Endocrine system

o    Hyperparathyroidism

o    Amenorrhea

o    Infertility

  1. Skin

o    Pruritus (itching)

  1. Electrolytes and acid-base balance

o    Hypervolaemia-overhydration


Hemodialysis usually takes place in dialysis units, which either operate autonomously or as individual departments in hospitals or clinics.

Home dialysis is very common abroad and patients are treated with the use of their own equipment at home.

Classic dialysis is performed three or four times a week. The duration of a session is usually 3 to 5 hours.

There are also various other forms of dialysis, such as the 8-hour overnight dialysis in France, extended nocturnal home dialysis (up to 6 nights a week) and daily short-term hemodialysis sessions.

We should also mention the different types of dialysis, such as on-line hemodiafiltration, which is a true breakthrough in nephrology and is used in all our centers.
In recent years, biotechnology focuses on finding improved forms of dialysis that simulate normal renal function as much as possible.
On-line hemodiafiltration is one such renal function replacement technique that combines both purification methods, diffusion and filtration and uses liquid solution, which is a sterile pyrogen produced during the dialysis session, as substitute.

The major indications for using this method are symptomatic hypotension episodes, especially for patients with impaired cardiovascular function, and better regulation of fluid loss in such patients, while several studies conducted in recent years found better cleansing levels of creatinine, urea and phosphorus and significant reduction of beta2 microglobulin, a substance that accumulates in hemodialysis patients and often causes bone pain.

All of the above show that on-line hemodiafiltration not only causes fewer episodes of symptomatic hypotension, but offers better quality of life and improves uremic polyneuropathy, and is likely to prevent dialysis-related amyloidosis. Finally, on-line hemodiafiltration is believed to contribute to the increase of life expectancy.

Usually, patients with chronic renal failure do not develop severe symptoms until renal function is reduced to 10-15%.
By this stage, decompensation can maintain basic bodily functions.

When kidney function falls below the threshold of 10 ml/min (less than 15 ml/min in diabetic patients), decompensation is no longer sufficient for maintaining normal bodily functions and renal function must be substituted.

Dialysis is a method that replaces renal function (the other two are peritoneal dialysis and transplantation).
This process uses the patient's blood, a filter and a special liquid solution through which waste accumulated in the body is discharged and useful ingredients are taken in.

Basically, this is a closed circuit that runs through the dialysis machine.
To achieve high blood flow, the vascular surgeon creates an arteriovenous (AV) fistula between the patient’s artery and vein.

Alternatively, if the patient's veins are not suitable, the surgeon can use a plastic graft between the artery and a larger vein or a catheter in a central vein (jugular or subclavian).
The advantages of hemodialysis include the ongoing contact with the doctor, three times a week sessions, and the fact that no special equipment is required at home.


Patients with chronic renal failure usually do not develop severe symptoms until kidney function decreases to 10-15%. By this stage, decompensation can preserve basic bodily functions.
When kidney function falls below the threshold of 10 ml/min (less than 15 ml/min in diabetic patients), decompensation is no longer sufficient for maintaining normal bodily functions and renal function must be substituted.

Dialysis is a method that replaces renal function (the other two are peritoneal dialysis and transplantation).

To achieve high blood flow, the vascular surgeon creates an arteriovenous (AV) fistula between the patient’s artery and vein.
Alternatively, if the patient's veins are not suitable, the surgeon can use a plastic graft between the artery and a larger vein or a catheter in a central vein (jugular or subclavian).
The advantages of hemodialysis include the ongoing contact with the doctor, three times a week sessions, and the fact that no special equipment is required at home.


Haemodialysis is the renal replacement therapy that is most frequently used today.
This process requires:

1.    A Vascular access, which is an arteriovenus fistula, a synthetic graft, or a haemodialysis catheter, either a temporary or a permanent one

2.    Needles and dialysis lines

3.    A haemodialysis filter

4.    A dialysis solution

Description of a haemodialysis session in simple words
The point of access to the patient’s circulation (fistula, graft or dialysis catheter) is connected to the machine via the haemodialysis needles or, in case of a catheter, via the blood lines.

The patient's blood contains metabolic waste products that are collectively called uremic toxins (urea, creatinine etc.) that need to be cleared. During haemodialysis, it is transferred through a special line (arterial line), with the help of a dialysis machine pump, to the dialysis filter. The filter is fabricated from a semi permeable membrane that selectively allows the exchange of molecules between the blood and the dialysis fluid. As the patient’s blood flows through the filter, uremic toxins are removed from it and are transferred to the dialysis solution (or dialysate).

Excessive water is removed at the same time.

The processed blood is returned to the patient via a second line (venous line).
This procedure is repeated several times during the session, leading to fluid and electrolytes balance and thus ensuring survival.

Direct access to the patient's circulation also enables intravenous administration of vitamins, erythropoiesis-stimulating agents and other necessary medications during a dialysis session. To achieve exceptional haemodialysis quality, all factors involved must be of top quality, starting from the filter.


Dialysis is an ongoing and repetitive process.

Patients must adjust to a new lifestyle that involves spending a lot of time in haemodialysis units, following specific diet rules and taking several medications.

Progress in infrastructure, with the establishment of Independent Dialysis Units based on high standards in terms of facilities, hygiene etc., has significantly improved the patients’ psychology and quality of life.

By quality of life, we mean the way we function within a society and how we experience the very existence of the human life.

The development of biotechnology and pharmaceuticals through the introduction of new high flux filters and new methods of on-line dialysis contribute to the prevention and suppression of complications of chronic kidney disease and function as a shield for the patient.

Modern dialysis regards patients as active members of society and in all aspects of everyday life (work, sports, studies, etc.).

Good quality of life is based on the fruitful cooperation between patients, doctors and nursing staff, and also on the philosophy of treating haemodialysis patients as valuable and separate entities.


Diet during dialysis is a very important factor for the survival and quality of life of the patients.
There are some basic nutrition principles, but diet must be individualized according to age, coexisting diseases, and the patient’s activity levels.

Basic diet rules

1. Balanced fluid intake

Depends on residual diuresis.
Normally, fluid intake is restricted and water intake through food is taken into account.
To manage thirst, patients are advised to limit salt consumption.
Risk of excessive fluid intake - pulmonary edema

2. Limited intake of foods rich in potassium 

Fruits and vegetables are rich in potassium. Their consumption must be limited and special preparation is necessary.

- Cut fruits and vegetables into small pieces of before eating.

- Peel off the skin of vegetables and fruits such as potatoes, tomatoes, carrots, apples, pears.

- Soak vegetables in plenty of water for at least two hours before cooking. Then rinse, boil for five minutes in plenty of water and drain.      
  Replace water and continue cooking as usual. 
  Risk of hyperkalemia and life-threatening arrhythmias.

3. Limited phosphorus intake

Foods rich in phosphorus are dairy products, legumes and cereals.
Phosphorus is excreted at a slow pace by failing kidneys, which leads to accumulation, and thus to hyperparathyroidism with skeletal and exoskeletal lesions that have a long-term effect on the patient’s quality of life and increase mortality rates.

4. Nutrition

The energy needs of renal patients basically depend on their physical activity but calorie intake for dialysis patients should be sufficient to prevent catabolism (breakdown of muscle tissue). As each person is unique, diet must also be individualized and adjusted accordingly while the patient’s social and financial status must also be taken into account.



There are many different conditions that can lead to kidney damage.
The most common cause of chronic kidney disease in developed and developing countries today is diabetes mellitus.

This condition, which has been characterized as pandemic, leads a sizable proportion of patients to the final stage of renal failure and dialysis.
Another common cause is hypertension, which also affects a large part of the population.
Glomerulonephritides are inflammatory kidney diseases that often cause renal failure, like pyelonephritis which may be due to an urinary tract infection, nephrolithiasis, obstructive disorders (adenoma or hypertrophy or prostate cancer, gynecological cancers, etc.), and vesicoureteral reflux.

Various drugs have been implicated in kidney damage (analgesics, anti-inflammatories, immunosuppressants, cytostatics, antibiotics, contrast agents, etc.), and poisonings (mushrooms, herbicides, heavy metals, etc.).
Hereditary nephropathies such as the adult polycystic kidney disease, Alport’s syndrome, and Fabry disease, as well as congenital diseases (renal dysplasia or hypoplasia, etc.).

Systemic diseases, such as lupus erythematosus or scleroderma, often lead to kidney failure.
Finally, neoplastic diseases (such as multiple myeloma), acute kidney failure, renal tuberculosis, kidney tumors, injuries or surgical removal thereof and perinatal causes (acute cortical necrosis, preeclampsia) are also some of the causes of renal failure.






6.    V.U.R.












Kidneys play an important role in metabolizing drugs and eliminating them from the body. If, for some reason, kidneys are not functioning, many medications are not normally excreted from the body and are accumulated in the blood leading to toxic effects.

Thus, the physician should reduce the dose of drugs administered in patients with renal impairment, depending on the magnitude of failure, and/or increase the dosing interval.

Nephrologists are of course the most experienced physicians in this case. On the other hand, many drugs affect renal function.

These drugs can aggravate an existing renal failure, or create a new one to previously healthy kidneys –either acute or chronic. For this reason such drugs are called nephrotoxic.

The most common nephrotoxic drugs are the non-steroidal anti-inflammatory drugs or NSAIDs. These are drugs taken every day by thousands of people who suffer from different sorts of musculoskeletal pain, but underestimate the risk to which they are exposed.

Most recent anti-inflammatory drugs are considered to significantly reduce the risk of kidney damage. In practice however, patients with renal impairment, hypertension, diabetes or even elderly patients should avoid them.

Other nephrotoxic drugs are the aminoglycosides. These are injectable antibiotics available under the following original names: amikacin, netilmicin, tobramycin, kanamycin, gentamicin and streptomycin.

Apart from acute renal failure they may also cause deafness. Drugs used in imaging examinations (CT scans, pyelography, angiography, etc.) are called iodinated contrasts and have nephrotoxic effects in some patients.

Chronic use of immunosuppressive drugs, such as cyclosporin and methotrexate, can be harmful to the kidneys. The same applies for antineoplastic drugs (such as cis-platinum), which may also cause permanent kidney damage. Many poisons are also harmful to kidneys.

Snake venoms, mushrooms and herbicides cause irreversible damage to the liver and kidneys.
The same applies for heavy metals, such as lead and mercury.




4.    NSAIDS






The best way to protect our kidneys is with proper nutrition and a healthy lifestyle. More specifically, our diet should mainly be based on vegetables and much less on meat. In other words, what we usually call "Mediterranean diet".

Foods should not be too salty, to prevent hypertension that destroys kidneys. You should drink enough water, not necessary bottled, but at least 1.5 to 2 liters a day, and even more during the summer. We must carefully monitor our weight. Avoid gaining weight and smoking that worsens kidney diseases. If we suffer from hypertension, we must regulate our blood pressure through diet and medication and in collaboration with our doctor.

The same applies if we have diabetes. Diabetes is the leading cause of kidney damage in developed and developing countries.
A diabetic patient should be examined by a specialized nephrologist at least once a year. Large-scale studies have shown that diabetics who were followed by nephrologists since the early stages of diabetes had better chances of avoiding dialysis compared to those who visited the doctor after developing advanced diabetic nephropathy.

Any tests that require iodinated contrast material (such as angiography, etc.) must be done with caution and only when absolutely necessary.
This is because the contrast material aggravate the kidney function, and even more in case of renal impairment.
Benefits versus risks must be evaluated.

In general, we should be very careful with all medicines prescribed to us. Some drugs directly damage kidneys (such as anti-inflammatories) and others only cause damage when administered in combination with other medication (for example some antibiotics in combination with diuretics).

We should also be very careful about any unknown substances we might be advised to take. If we suffer from some degree of renal insufficiency, we should always inform our doctor before any prescription medication, in order to avoid iatrogenic kidney damage due to unawareness of medical history.



Other techniques include dialysis and transplantation. All three methods are effective, but choosing the appropriate one depends on a number of factors that relate to both the patient and the availability of technical, human and material resources.
All three methods use some type of filter for blood clearance. In dialysis the filter is fully artificial. In transplantation it is 100% natural (transplanted kidney) and in peritoneal dialysis it is natural, yet placed in a different part of the body. 
Peritoneal dialysis uses the patient’s peritoneum as a filter. The peritoneum is the biological membrane that covers the internal abdominal wall, and then folds and fully covers the internal organs.
This creates a space, the so-called peritoneal space, that looks and behaves like a slightly inflated balloon we hold in our hands. The technique involves the injection of the right volume and composition electrolyte solution in the peritoneal cavity, so as to provide the body with the necessary substances and to eliminate excess contents and water.
When treatment is completed and harmful substances and excess fluid are exchanged, the solution is removed and replaced with fresh. Access to the peritoneum is achieved with a peritoneal catheter which is a special stent made of biocompatible materials with specific morphology. It is implanted either surgically or through puncture or laparoscopically at a suitable position inside the peritoneal cavity. Fluids are infused either manually or with the use of equipment.
The manual method uses dialysate bags that the patient handles himself. Fluids must be infused and then excreted from the peritoneum usually four times every 24 hours.The automated method uses a machine programmed to follow fluid infusion and drainage cycles over a certain period of time, so as to allow 4 to 6 exchanges during the night while the patient is asleep.In this case patients and their relatives must be deeply involved in the process and also wanting to be.
The patient will have to follow a thorough training session at the Peritoneal Dialysis Department of a hospital, and must be informed, and provided with instructions to face any problem that may occur.He can be in contact with the unit on a 24-hour basis for advice or anything else he may need, and can be admitted if the problem is difficult to handle.
Strict adherence to the instructions provided by the unit’s personnel and meticulous care on the patient’s behalf during treatment can ensure that treatment will continue over time.
Over time, however, the peritoneum hardens and the treatment outcome is less successful; something that requires a change of method.
Advantages of this method include:Advantages of this method include:


1.    Critical participation of the patient in treatment,

2.    More freedom in fluid intake,

3.    Prevention of hypotensive episodes thus allowing longer preservation of residual renal function.

4.    Maintaining diuresis for a longer time, especially if the method is, chronologically speaking, the first option for renal replacement.

5.    Use of this method for ensuring autonomy in case the patient wishes to travel in areas where there are no dialysis units or in inaccessible
       and remote areas where scheduled dialysis methods cannot be supported.

6.    Use of this method in patients with no vascular access options.

This method’s disadvantage is that over time the peritoneum hardens due to the heavy burden and does not perform as well as in the beginning. Due to insufficient dialysis, the patient needs to change treatment method. Also, it is not advisable for patients with impaired vision and mobility problems, especially in the hands. The method’s reduced availability is also an obstacle.



A kidney transplantation is the treatment of choice for patients of end stage renal disease. Kidneys come from living donors or brain dead or recently cadaveric donors. The term "brain death" means death of the cerebrum. All patients at end stage kidney disease are theoretically eligible for kidney transplantation. Although a relatively simple operation, a kidney transplantation is not a simple task, neither for the recipient nor for the medical team.
After transplantation, the patient must be submitted to strong immunosuppressive treatment (e.g., steroids, cyclosporine, azathioprine, mycophenolate, tacrolimus, rapamycin, antibody treatment). To avoid complications, the kidney transplant recipient must be evaluated by the medical team prior to the operation to ensure eligibility for this procedure. Further to the detailed medical history of the potential recipient, a detailed clinical examination is also necessary along with an extensive lab and radiological evaluation. The existence of any mental disease must also be excluded. Same applies for rectal bleeding and coronary heart disease. 
Men over the age of 40 should have their prostate examined. Women must undergo a Pap test, pelvic examination and, when over 40 years of age, they must also have a mammography performed. Smokers should quit smoking.
The lower urinary tract should be sterilized prior to transplantation, as confirmed by a complete urinalysis and urine culture. A cystography and urodynamic testing must be performed in case of suspected genetic abnormalities.Vesicoureteral reflux should be corrected prior to transplantation.

Also before transplantation, patients must be submitted to surgical procedures necessary for treating the following cases:

Nephrectomy: Large polycystic kidneys (contralateral), chronic parenchymal inflammation, chronic inflammatory reflux, severe proteinuria, uncontrolled hypertension, inflammatory nephrolithiasis

Splenectomy: Donor/ recipient blood group incompatibility (ABO) 

Cholecystectomy: Cholelithiasis

Colectomy: History of diverticulitis

Prostatectomy: Prostatic hypertrophy, which can cause obstructive uropathy to the graft

Coronary revascularization: Coronary disease

Contraindications for kidney transplantation:

Cirrhosis (except in combined liver-kidney transplantation)

Chronic respiratory failure (risk during general anesthesia)

Severe peripheral vascular disease

Active peptic ulcer (until treated, with medication or surgery)

Coronary artery disease (treatment before transplantation with angioplasty or CABG)

Irreversible congestive heart failure (unless a combined kidney-heart transplantation is performed)

Active systemic lupus erythematosus

Active human immunodeficiency virus (HIV) infection

Active chronic inflammation (osteomyelitis, gravitational ulcers in diabetics, active tuberculosis, recurrent urinary tract infections, peritonitis)

Patients positive for hepatitis B (increased risk of death due to resurgence of viremia after transplantation due to immunosuppression)

Uncontrolled cancer

Psychiatric disorders

Non-compliance to previous treatment (high-risk patients for graft loss due to poor treatment compliance)

Blood group incompatibility (ABO) (increased risk of accelerated or hyperacute rejection)

HLA incompatibility (the better the compatibility antigens HLA-A, HLA-B, HLA-DR between donor and recipient, the better the outcome of transplantation)

Cross-compatibility (cross-matching) when positive transplantation is not permitted due to increased risk of vascular and hyperacute rejection in the early post-transplant period.

A man can live a normal life with one kidney. However, after a kidney transplant strict adherence to treatment is necessary. Regular laboratory tests for monitoring the functioning of the transplanted kidney and the levels of various drugs are necessary to avoid unwanted complications.

Complications following a transplant are divided into early and late. 
Early complications involve poor kidney function, possibly because of acute rejection, cyclosporine toxicity, ischemia prior to kidney revascularization due to prerenal and postrenal problems, cytomegalovirus or Ebstein-Barr infection. 

Late complications involve the loss of kidney function as a result of chronic rejection or recurrence of primary disease in the graft, hypertension, hyperlipidemia, osteoporosis, skin cancer, lymphomas, Kaposi’s sarcoma, genital tract tumors, peptic ulcer, psychiatric disorders, diabetes mellitus, cardiovascular problems and others conditions.
In the past the most appropriate time for transplantation from a living donor was after the patient’s start the renal function replacement therapy.
Lately, patients are advised to proceed to kidney transplantation before starting renal function replacement therapy  .
Namely, when creatinine clearance is equal to 10 ml/min or 15 ml/min for children and diabetics.
This means when the patient’s overall health condition is still good, but their kidney function is poor enough to require transplantation.
As to potential transplant recipients from living or cadaveric donors, and in order to ensure best outcome of a future kidney transplantation, strict adherence to medication and adequate renal function replacement therapy is advised (hemodialysis or peritoneal dialysis).
The text was edited by the MESOGEIOS Medical Board:
George Dimitriadis, Aristidis Paraskevopoulos, Fotis Makris, Theodoros Pliakogiannis, Thenia Papagiannidou, Anastasios Poulopoulos, Kalliopi Retsa