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To receive a kidney is an incredibly valuable gift, whether as a living donation from a loved one or through a deceased person. Many people with kidney failure see a transplant as a relief from dialysis and hope to regain a little more normality in their daily lives. So it's all the more important to take good care of your new organ. Here you can find out exactly how the function of your new kidney is monitored and which values are particularly important for you and your medical team.
Here's what you need to know
Das solltest du wissen
Ecco cosa c'è da sapere
Voici ce qu'il faut savoir
Esto es lo que debe saber
  • The most important laboratory values after transplantation include creatinine, cystatin C, urea, hemoglobin (=Hb), potassium, phosphate and the estimated glomerular filtration rate (=eGFR).
  • It is often completely normal that certain laboratory values are not quite within the normal range immediately after transplantation. In the beginning, the most important thing is that they do not fluctuate too much.

  • In order to recognize a possible decrease in the performance of your kidney at an early stage, you should also pay attention to symptoms such as water retention, reduced urine excretion, pain in the area of the new kidney, etc.
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The kidneys are true jack of all trades. When healthy, they work around the clock to keep your blood and your body fit and balanced. But that's not all! At the same time, they also balance your blood pressure and release hormones such as erythropoietin (=EPO), which stimulates the formation of new red blood cells. Kidneys are real pros at multitasking.

It's no wonder that kidney failure requires intensive monitoring and therapy in the form of dialysis, nutritional adjustments and medication to take over these tasks in the best possible way. After the transplant, your new kidney is once again responsible for all of this.

Of course, this presents your body with new challenges that need to be mastered. After all, your new organ must be introduced into your body via surgery, accepted by your immune system and then function properly. Especially the first months after the transplantation are an adjustment for you and your new kidney. However, this is no reason to worry - in the vast majority of cases you will also master this task. To give you the best possible support along the way, there are a number of tests and examinations that your medical team will use to keep a regular eye on the function of your new kidney during its journey. You can find out exactly what these tests are and how they work in this article.

What functions does my kidney transplant take on in the body?

As you already know, your new kidney takes on a whole range of tasks in the body. Their most important functions are summarized here for you:

  1. Filter function: Your new kidney filters out a whole range of breakdown products and harmful substances, such as creatinine, from your blood. These are then excreted through your urine.
  2. Water balance & blood pressure: Your transplant ensures that your water balance remains in equilibrium. Water can either be retained in your body or excreted through your urine. The same applies to electrolytes. For your water balance - and thus also for your blood pressure - the electrolyte sodium (e.g. contained in table salt) is particularly relevant. Your kidneys therefore also play a major role in regulating your blood pressure.
  3. Hormones: Your kidney produces important hormones, such as erythropoietin (=EPO), which stimulates the formation of your red blood cells. These transport oxygen through your blood to all parts of your body.

Below you will learn how these individual functions are monitored through a series of values, laboratory parameters and symptoms. They are used to regularly monitor the health of your transplant.

What are important lab values for monitoring my kidney transplant?

After the transplant, the function of your new kidney will be regularly monitored by laboratory values. These will be taken and checked either by your transplant team or by your nephrologist. This is useful because changes in your lab values can also indicate early changes in your kidney function - sometimes before you notice them yourself.

You can also always document your most important lab values in your logbook in the Mizu app. Of course, you should always discuss any questions or irregularities in your lab results with your medical team instead of trying to make any therapeutic adjustments on your own. Below we have summarized an overview of the most important lab values for monitoring your kidney function:

1. Creatinine

Creatinine is a breakdown product from muscle metabolism. It is excreted through your kidney. If your new kidney does not function as it should, the creatinine level in your blood will increase. Of course, your exact creatinine level also depends on your muscle mass. So creatinine tells you how well your kidney can filter the harmful substances out of your blood.

The target values for your creatinine depend on your sex at birth. For healthy women, the target level is between 0.5 and 0.9 mg/dL. For healthy men, the target level is between 0.7 and 1.2 mg/dL. But don't worry if your levels are slightly higher after transplant. This is often not uncommon and your medical team will keep an eye on it. After transplant, the main thing is to avoid large fluctuations or increases in creatinine levels. The goal is a level that is not too high and remains stable over time.

2. Urea & urea-N (=BUN)

Similar to creatinine, urea is a breakdown product. It comes from your protein metabolism and is largely excreted through your urine. A high urea value therefore also indicates a lower excretion via your kidneys and thus a decrease in kidney function. Depending on the laboratory, either urea or the nitrogen contained in urea (=urea-N) is measured. Although the target values may differ depending on the measurement method, both values have the same meaning.

The target values for urea-N (also called BUN) in healthy people are between 6 and 20 mg/dL or 2.1 and 8.9 mmol/L, while those for urea are between 13 and 54 mg/dl. In mmol/L, urea and urea-N have the same target range of 2.1 - 8.9 mmol/L. After transplantation, this value may also be slightly higher than normal.

3. Cystatin C

Cystatin C is a protein in your blood. In a healthy state, it is filtered out of your blood by your kidneys and broken down there. In this way, your kidney keeps the cystatin C level in your blood in balance. If the filtering function of your kidney decreases, the cystatin C value increases - very similar to creatinine. Therefore, cystatin C is also considered an indicator (a so-called "marker" or value) that can be used to determine the filtering function of your new kidney.

The target values for cystatin C are between 0.5 and 0.95 mg/L for healthy men and between 0.55 and 0.95 mg/L for healthy women. Again, levels may well be somewhat higher after transplantation.

4. Estimated glomerular filtration rate (=eGFR)

The estimated glomerular filtration rate tells you how much blood your kidney filters per minute. It is not a separate value, but is calculated. Among other things, the creatinine or cystatin C value is needed for the calculation. In the Mizu app, you can enter your eGFR directly.

In chronic kidney insufficiency, this value allows a classification into roughly five different stages. As the function of the kidneys decreases, the eGFR also decreases from stage 1 to stage 5. If the eGFR is below the value of 15 mL/min (=stage 5), this is called renal or kidney failure. Even after transplantation, the eGFR is still used to monitor how well your new kidney is working.

Stage of kidney failure GFR (mL/min)
G1 ≥ 90
G2 60 - 89
G3a 45 - 59
G3b 30 - 44
G4 15 - 29
G5 < 15

After transplantation, your eGFR does not necessarily have to be üabove 90 ml/min again. In fact, few people reach this value after transplantation. It is more important that your eGFR is not significantly reduced and - as with the other values - reaches a stable level. In general, after transplantation, for many values, the progression over time is more important than the exact value on a cutoff date.

5. Protein in urine

Normally, only very small amounts of protein are excreted in the urine by a healthy kidney. This is also the case with your new kidney. Of course, your new kidney has already been through something. It had to be taken from another body, brought to you and then surgically transplanted into your body. It can happen that your new kidney excretes a little more protein than usual.

The reference range is less than 150 mg of protein in the urine per day. As mentioned before, the excretion can be somewhat higher with your new kidney. As is often the case, a single value is not as decisive as the course over several measurements.

6. Potassium, phosphate & Co.

After transplantation, there are often no dietary restrictions on potassium and phosphate - at least as long as your kidney is working properly. Especially directly after the transplantation, your potassium and phosphate values may still fluctuate relatively strongly and have not yet stabilized. Therefore you should also keep an eye on these values.

Your phosphate level should usually be lower than 1.45 mmol/L (or 4.5 mg/dL) after transplantation. For your potassium level, the target range is 3.5 to 5.0 mmol/L. If your levels are high or low, adjustments to your diet can help manage your levels. However, as always, it is best to discuss exact target values and guideline corridors with your medical team. They know your individual health best.

7. Hemoglobin (=Hb)

Hemoglobin (=Hb) is the red blood pigment in your blood cells. If your new kidney does not secrete enough EPO, the number of red blood cells and thus the amount of hemoglobin in your blood will drop. In this case, it is called anemia. It is worth keeping an eye on this value as well.

The target values for hemoglobin are 13 to 17 g/dL for healthy men and between 12 and 15 g/dL for healthy women. Again, values may well vary slightly after transplantation. In the case of hemoglobin, it is more likely that it will still be too low initially. As always in medicine, there are of course other causes that can lead to anemia, such as iron deficiency or blood loss during surgery.

What does the excretion reveal about my kidney function?

As you already know, your kidney is also responsible for a stable water balance. The human body consists of up to 70% water. So it's no wonder that your kidney has its hands full keeping this water in balance through your urine.

If your kidney stops working as it should, more water will collect in your body. This can have various consequences:

  • less urine output than normal
  • increased blood pressure
  • water retention (=edema) for example in the legs or also in the lungs
  • rapid weight gain due to water retention

To keep an eye on your water balance, your medical team will collect your urine in a bladder catheter immediately after your transplant. In this way, your daily urine production can be closely monitored. If your kidney needs some time to get back into gear, you may be required to undergo supportive dialysis after the transplant. Don't worry, this is just a precaution.

Once you are home, you can also check your urine production regularly using a collection canister. Simply collect your urine over 24 hours in this canister. Remember, however, that your excretion also depends on the amount you drink, your sweat production and other factors (e.g. diarrhea). A so-called balance will help you to determine whether your water intake and your excretion are in equilibrium. This in turn tells you whether your new kidney is working well. You can find out exactly what this balancing is and how it works in the other articles of the Mizu app.

In the Mizu app, you can also document your weight and blood pressure. While the target values for your weight naturally depend on your individual values, your blood pressure should generally be below 130/85 mmHg after transplantation. In this case, too, it is best to talk to your medical team, who will tell you your personal target values.

What symptoms should I look out for?

If your kidneys can no longer filter your blood sufficiently, water retention may occur. This can lead to edema in your legs or arms, for example. This water that collects in your body then also leads to a higher body weight. Therefore, it makes sense to weigh yourself regularly after the transplant.

In addition to water retention, your immune system may also reject your new kidney after the transplant. This is when your body's immune cells recognize the transplant as a foreign body. Symptoms include:

  • Fatigue and fatigue
  • Fever and increase in body temperature
  • Decreased urine output
  • Increased blood pressure
  • Pain in the area of the new kidney

A rejection does not always lead to a loss of your transplant. It is important that your medical team can respond quickly. You can help your transplant team recognize and treat a rejection early by regularly documenting values such as temperature, urine output, weight and blood pressure in your Mizu App logbook.

Why might my new kidney not be working?

The reasons for a decline in kidney function after transplantation are varied, but not always dramatic. It is important to recognize the decline in kidney function early so that the appropriate treatment can be initiated. It is therefore all the more important for you to know which values you should pay attention to.

Possible reasons for a decrease in the function of your new kidney include:

  • Rejection reactions by your immune system
  • Infections caused by pathogens when your immune system is weakened (=immunosuppression)
  • Recurrence of your underlying disease
  • Too high immunosuppression levels

You can find out exactly what these individual factors are in many other parts of the Mizu app. In these, we have summarized detailed information on each of the topics for you.

How do I keep my new kidney healthy?

Up to 49% (but the frequency varies widely) of new kidneys after post-mortem donation and 8% of new kidneys after living donation need some time to fully arrive in their new home and function properly. After one year, about 90% of all new kidneys function as intended and often last for up to 15 years with mindful handling. These numbers illustrate how well kidney transplantation now works and spur us to be as careful as possible with our precious new organ.

To best support the function of your new kidney and keep your new organ healthy, you should place special emphasis on a healthy lifestyle. This includes a healthy weight, proper diet, exercise, normal blood pressure and taking your medications reliably. If you also attend regular check-ups at your center, almost nothing can go wrong. To find out exactly what behaviors are right for you and what to look for in your diet, check out many more resources and articles in the Mizu app.

Medically reviewed by:
Medizinisch überprüft durch:
Verificato dal punto di vista medico da:
Médicalement vérifié par :
Médicamente comprobado por:
Dr. Diego Parada Rodriguez (en)
Specialist in training for Nephrology
References
References
References
References
References
  • Kidney Disease: Improving Global Outcomes (KDIGO) Transplant Work Group. KDIGO clinical practice guideline for the care of kidney transplant recipients. Am J Transplant. 2009 Nov;9 Suppl 3:S1-155. doi: 10.1111/j.1600-6143.2009.02834.x. PMID: 19845597.
  • ERA Registry Annual Report 2020
  • OPTN/SRTR 2019 Annual Data Report: Kidney
  • Redfield RR, Scalea JR, Zens TJ, Muth B, Kaufman DB, Djamali A, Astor BC, Mohamed M. Predictors and outcomes of delayed graft function after living-donor kidney transplantation. Transpl Int. 2016 Jan;29(1):81-7. doi: 10.1111/tri.12696. Epub 2015 Oct 26. PMID: 26432507.
  • Lehner LJ, Hohberger A, Marschke L et al. Impact of delayed graft function and number of dialysis sessions on graft outcome after kidney transplantation. Am J Transplant 2015; 15(Suppl 3): abstract 440
  • Gilbert, SJ. et al (2022). National Kidney Foundation Primer on Kidney Diseases (8. Aufl.). Elsevier.
  • lmu-klinikum.de. Nierentransplantation. Abgerufen am 16.01.2023
  • transplantation-verstehen.de. Komplikationen: Diese Probleme kann es nach der Nierentransplantation geben. Abgerufen am 16.01.2023
  • uniklinik-freiburg.de. Nierentransplantation. Abgerufen am 16.01.2023
  • kdigo.org. Blood Pressure in CKD. Abgerufen am 16.01.2023
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