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PART I
Epidemiology and Acceptable Rates of Complications Following Thyroid and Parathyroid Surgery
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CHAPTER 1
Incidence of Morbidity Following Thyroid Surgery: Acceptable Morbidity Rates
Paolo Miccoli,1 Michele N. Minuto2 and Mario Miccoli3
1 Department of Surgery, University of Pisa, Pisa, Italy
2 Department of Surgical Sciences (DISC), University of Genoa, Genoa, Italy
3 Department of Experimental Pathology, University of Pisa, Pisa, Italy
Introduction
The issue of complications in surgery is a very difficult topic to deal with. Few surgeons speak openly about their problems, many are tempted to under-rate their own incidence, and even debates in the most important Âinternational circles about complications may fail to fully encompass the scope of the problem.
Unfortunately, since the dawn of surgery, Âcomplications have been inescapable, although undesired, elements of the surgical discipline but they have also allowed surgery itself to constantly improve.
In the new century, surgeons should deal with patients undergoing surgery under their care in a Âcompletely Âdifferent way. The road leading to the Âoperation itself starts well before surgery, when the patient is informed about his operation, the way it will be performed and the possibility and incidence of Ârelevant complications. The number of complications that a surgeon generally shares with the patient before surgery requires judgement; informed consent should be obtained after a thorough discussion of the common problems that might occur after surgery, starting from the possibility of a keloid scar (an event that is usually not related to the surgeon) to intraoperative or Âpostoperative death, more often Âunrelated to surgery but due to other co-morbidities.
In between these two exceptional events, there is the real intraoperative complication that is directly or Âindirectly caused by the surgeon (iatrogenic) but that is not Ânecessarily due to negligence.
Modern surgeons should be aware of how to deal with the complication and therefore instruct and start to treat the patient themselves or, at the very least, to correctly refer the patient to a relevant specialist.
In thyroid surgery, complications that may arise after surgery may vary from those that might be immediately life-threatening but resolve after proper treatment, often leaving no sequelae, to relatively minor problems that are immediately evident and can therefore cause significant impairment of the patientâs quality of life. The management of those patients experiencing post-thyroidectomy sequelae can be difficult, and this book contains suggestions to help every surgeon properly manage their own patients both intra- and postoperatively, helping them to determine the possible options to deal with a selected complication.
Morbidity of thyroid surgery
Every experienced surgeon is aware that the incidence of intra- or postoperative complications in thyroid surgery is relatively common, starting from the âfrequentâ postoperative hypoparathyroidism (transient in the vast majority of cases) that in some reports has a frequency as high as 53% [1, 2].
The relative rarity is also dependent upon the method of analysis: although the single morbidity (e.g. permanent recurrent nerve injury) may be uncommon, when Âlooking at the total incidence of the complications as a whole, the incidence of morbidity rises sharply. The rarity of a complication is also strictly related to the overall activity of the surgical practice (and therefore to the experience of the surgeon); a surgeon performing 10 Âthyroidectomies every week may see an injury of the recurrent nerve more often than another good surgeon who performs 60 thyroidectomies per year, even if the first is unquestionably more experienced than the Âlatter.
The literature contains many series with an almost 0% incidence of complications that cannot be considered straightforward. How can this happen? Every Âexperienced thyroid surgeon is perfectly aware of the issues behind such a low incidence of complications, but an Âinexperienced one might be misled by the results, and legal operators and lawyers might use them to manipulate facts, twisting the relatively common events and turning them to an evidence of malpractice.
We would therefore like to address the complications issue in a different way than that of a single experience reported in literature, aiming to show every surgeon how to interpret the commonly reported results, and how a sound and thorough study of complications should be conceived, in our opinion.
- When dealing with a specific complication of thyroid surgery, it is necessary to contrast our own incidence of the single event with the general incidence as reported in literature; this comparison should be made with series that are similar in terms of numbers. Going deeper into the issue, a 0% incidence of a selected Âcomplication in a series of 100 patients is a good result indeed, but if the event in question has a very low Âincidence, this does not represent a significantly different result from that obtained by another surgeon who reports a single one.
- This leads to the issue of statistically significant Ânumbers, which will be better developed later in this chapter. Due to the fact that a complication is a relatively uncommon event, when analysing the results reported by other authors, the series should have sufficient numbers to have statistical relevance. It is easy to understand that a 0% incidence of permanent recurrent nerve lesions, reported in a prospective series of 33 patients in a study designed to investigate the oncological thoroughness of minimally invasive video-assisted thyroidectomy versus Âconventional thyroidectomy, cannot be interpreted as a statement that the rate of recurrent nerve palsy in thyroid surgery for cancer should be 0, for example. Since the paper was not planned to investigate the incidence of complications, the numbers are clearly too limited for this. Nevertheless, it was necessary to report this result in the paper, since it has an important clinical (but no Âstatistical) value.
Further in this chapter, we give the readers some Âinformation about how to interpret statistical data from the literature, and introduce some basic statistical notions on uncommon events such as surgical complications. These simple concepts should be the basis of any audit conducted within a surgical unit.
Acceptable rates of thyroid surgery complications
We will hereafter deal only with the two principal complications of this surgery: recurrent nerve injury (RNI) and hypoparathyroidism. All other issues will be thoroughly analysed in the relevant chapters. The data reported will be drawn from the most important experiences (strictly in terms of number of patients analysed) available from the literature.
Injury of the inferior laryngeal/recurrent nerve
This complication is generally considered the worst for its potential impact on the patient immediately after surgery and for its significant consequences on the patientâs future quality of life. The event causes a major impairment in one of two situations: the voice (with the onset of typical dysphonia) or the ventilation, and the related symptoms are Âgenerally present in an inverse ratio. When analysing the incidence reported by various authors, the reader should be aware of the following parameters.
- The series should take into consideration a significant number of patients (see after in this chapter), and one should be aware that the incidence reported can be obtained from the total number of patients in the study or from the total number of nerves at risk (that may Âdouble the sample, if only patients undergoing a total Âthyroidectomy have been selected for the analysis).
- Is the series mixing cases of thyroidectomies for benign and malignant diseases and primary and reoperative Âsurgery? The incidence of a RNI (as well as of hypoparathyroidism) is invariably higher when a thyroidectomy for cancer (possibly associated with a central neck dissection) is performed or when the operation comes after a previous surgery. The morbidity is also significantly increased when performing a thyroidectomy for a particularly aggressive cancer subtype; the more aggressive the tumor, the higher the possibility of RNI, as described by a multicentre study that includes almost 15,000 patients [3].
- Have the authors reported whether their results were calculated on the basis of routine postoperative laryngoscopy or only on the basis of the postoperative discomfort or voice alteration of the patient? It is well known that a RNI can exist also in the presence of a remarkably normal voice. Also, a preoperative laryngoscopy should be Âperformed in every patient undergoing thyroidectomy, since evidence of preoperative paralysis of a vocal cord is present in as many as 1.8% of patients; although in the majority of them it relates to previous surgery, the rate of this unexpected finding is still significant (six out of 14 patients without any previous surgery in the series described by Echternach et al.) [4]. When either pre- or postoperative laryngoscopy is absent, the real incidence of RNI will be significantly affected, decreasing when a postoperative laryngoscopy is not routinely performed and, on the other hand, unjustly assigning complications to the surgeon when such a preoperative examination has not been done.
- Finally, when reporting the incidence of RNI, one should always check if the patients have been followed up for at least 6 (or 12) months, to have the possibility of dividing the transient lesions (that last for 12 months at the longest and then spontaneously resolve, leaving no sequelae) from the permanent ones.
An analysis of selected papers dealing with more than 500 cases [3â12] is summarized in Table 1.1. These represent the most reliable papers dealing with the incidence of complications following thyroid surgery. These published data allow one to show either a high or a low incidence of RNI following thyroid surgery; it is immediately evident that the results demonstrate wide variability in the Âincidence reported by experienced thyroid surgeons.
Table 1.1 Reported incidence of transient and permanent RNI in studies considering more than 500 patients.
|
| Lo et al. [11] | 500/787 | 5.2/0.9 |
| Toniato et al. [7]â | 504/1008 | 2.2 |
| Chiang et al. [10] | 521/704 | 5.1/0.9 |
| Steurer et al. [12] | 608/1080 | 3.4/0.3 (benign disease) |
| | 7.2/1.2 (malignant disease) |
| Lefevre et al. [9]§ | 685/n.a. | n.a./1.5 |
| Efremidou et al. [6]* | 932/1864 | 1.3/0.2 |
| Echternach et al. [4] | 1001/1365 | 6.6 |
| Bergamaschi et al. [5] | 1163/2010 | 2.9/0.3 |
| Thomusch et al. [8]* | 7266/13436 | 2.1/1.1 |
| Rosato et al. [3] | 14934/n.a. | 3.4/1.4 |
Recurrent nerve injury has an incidence ranging from 0.3% described by Bergamaschi et al. [5] to 6.6% reported by Echternach et al. [4]. When we analyse their results more carefully, we can observe that Bergamaschi et al. report on a huge series (1192 operations and 2010 nerves at risk), dominated by benign disease (>90%) and Âreflecting a majority of patients who underwent less than total thyroidectomy (622), an operation that is less Âmorbid than a total thyroidectomy. In contrast, the series reported by Echternach et al. reveals a significantly higher rate of RNI, but this result does not take into account the rate of transient and permanent lesions, since it does not have laryngoscopy follow-up 6 months after the operation, and therefore it cannot be used for a proper analysis of permanent RNI. In between these two extremes, the real and expected incidence of RNI exists.
When we consider the different series homogeneously, we can see how the reported incidence of RNI is similar for any experienced thyroid surgeon. In the studies reporting exclusively on benign diseases, the incidence appears very low (0.2% according to Efremidou et al. [6], who report their results ...
